Calculators
Online Calculators
314 tools
Browse by subject, or search the full catalog.
Browse by subject
Nine current product categories. Family pages live under Electrical first.
- Grade GPA, final grade, and letter grade conversions.
- Math Arithmetic, percentages, trigonometry, and more.
- Wire Wire gauge, AWG/SWG, and voltage drop.
- Electrical Amps, volts, watts, kVA, and power tools.
- Physics Mechanics, energy, thermodynamics, waves, and optics.
- Chemistry Amount of substance, solutions, and acid-base pH.
- Engineering Tolerance, uncertainty, and engineering analysis tools.
- Time Age, dates, duration, and world clocks.
- Financial Interest, VAT, GST, and related finance tools.
- Lighting Lumens, lux, candela, and lighting conversions.
Popular calculators
High-traffic and flagship tools. Registry featured list.
- Ohm's Law Calculator Enter any two of voltage, current, resistance, and power to solve the remaining values. Runs locally in your browser. Free online tool — no sign-up.
- Watts to Amps Calculator Convert watts to amps (and reverse) for DC, single-phase, and three-phase circuits. Power factor and voltage inputs included for AC loads. Try it free.
- Smith Chart Calculator Interactive impedance Smith chart with auto-match, drag-to-tune, L·C·R / T-line / stub / transformer / ‖RLC, Custom Z(f), f-locus, and Touchstone S11/S21 with stability overlays. Runs locally in your browser.
- Free-Space Path Loss Calculator Compute free-space path loss FSPL = 20·log10(d·f) + 20·log10(4π/c) from distance and frequency, with optional antenna gains. Runs locally in your browser.
- Voltage Divider Calculator Solve a two-resistor voltage divider: enter exactly three of Vin, R1, R2, and Vout to find the fourth. Also reports current, power, ratio, and Rth. Try it free.
- Percentage Calculator Calculate percentages, percentage of a number, and “what percent is X of Y” with clear arithmetic steps. Runs locally in your browser. Try it free.
- Uncertainty Propagation Calculator Propagate measurement uncertainty using GUM linear propagation, covariance, uncertainty budgets, or Monte Carlo simulation. Optional correlation ρ and coverage factor k → U. Runs locally in your browser.
- GPA Calculator Calculate GPA from letter grades and credit hours using a 4.33 or 4.0 reference scale, with an optional Custom A+ value. Runs locally in your browser. Free online tool — no sign-up.
Grade calculators
GPA, final grade, and letter grade conversions.
- Final Grade Calculator Find the score you need on a final exam, compute your overall grade after the final, run a weighted category average, or convert point totals into final.
- GPA Calculator Calculate GPA from letter grades and credit hours using a 4.33 or 4.0 reference scale, with an optional Custom A+ value. Runs locally in your browser. Free online tool — no sign-up.
- GPA to Letter Grade Calculator Approximate GPA-to-letter interpretation on plus/minus 4.33, flat 4.0, or linear 5.0 normalization, with explicit tie-breaks, example percentage bands, and range validation.
- Letter Grade to GPA Calculator Convert a letter grade (A+ to F) to published grade points on plus/minus 4.33 or flat 4.0. Optional credits show quality points for one course.
Math calculators
Arithmetic, percentages, trigonometry, and more.
- Antilog Calculator Calculate the antilogarithm: raise base b to power y. Fast local calculation with shareable, machine-readable results.
- Arccos Calculator Calculate arccos(x) = cos⁻¹(x) for x in [−1, 1]. Fast local calculation with shareable, machine-readable results.
- Arcsin Calculator Calculate arcsin(x) = sin⁻¹(x) for x in [−1, 1]. Fast local calculation with shareable, machine-readable results.
- Arctan Calculator Calculate arctan(x) = tan⁻¹(x) for any real x. Fast local calculation with shareable, machine-readable results.
- Circle Calculator Compute diameter, circumference, and area from r, or arc and sector from a central angle. Not the Pythagorean page. Runs locally.
- Complex Number Calculator Add, subtract, multiply, divide complex numbers; convert rectangular ↔ polar. Not a CAS. Runs locally.
- Coordinate Geometry Calculator Distance, midpoint, and slope of two points in the plane. Not the Pythagorean-only page. Runs locally.
- Cos Calculator Calculate cos(θ) in degrees or radians. Fast local calculation with shareable, machine-readable results.
- Definite Integral Calculator Composite trapezoid or Simpson 1/3 of a polynomial, sin, or exp on [a, b]. Not indefinite symbolic integrate. Runs locally.
- Division Calculator Divide numbers with quotient, remainder, and decimal results for quick arithmetic checks. Runs locally in your browser. Free online tool — no sign-up.
- Exponent Calculator Calculate aⁿ for a real base and exponent. Fast local calculation with shareable, machine-readable results.
- Exponential Growth Calculator Model exponential growth or decay from initial value, rate, and time. Runs locally in your browser. Free online tool — no sign-up. Try it free.
- Factorial Calculator Calculate n! for integers 0 ≤ n ≤ 5000. Fast local exact integers with shareable, machine-readable results.
- Fractions Calculator Add, subtract, multiply, or divide fractions and mixed numbers with step-by-step LCD work. Free online tool — no sign-up. Runs locally in your browser.
- GCF Calculator Find the GCF, GCD, or HCF of two or more integers. Exact BigInt Euclidean fold with factor and prime cross-checks. Free, no sign-up.
- LCM Calculator Find the LCM of two or more integers with exact arithmetic and independent verification. Free, no sign-up.
- Linear Equation Calculator Solve ax + b = rhs for x. Identity and inconsistent cases when a = 0. Not the quadratic formula. Runs locally.
- Linear System Calculator Solve small linear systems Ax = b, plus determinant, inverse, and multiply. Same engine as the matrix workspace. Not a CAS. Runs locally.
- Log Calculator Evaluate logarithms (common, natural, or arbitrary base) for x > 0. Fast local calculation with shareable, machine-readable results.
- Modulo Calculator Integer remainder with a = q·m + r and 0 ≤ r < |m|. Euclidean convention, not JavaScript truncated %.
- Multiplication Calculator Multiply two numbers instantly, or see long multiplication with partial products, carrying, decimals, and sign rules. Runs locally in your browser.
- Natural Log (ln) Calculator Calculate ln(x) = log_e(x) for x > 0. Fast local calculation with shareable, machine-readable results.
- Numerical Root Calculator Find a real root of a polynomial with Newton, bisection, or secant. One capability, three methods. Not the nth-root page. Runs locally.
- Percent Error Calculator Compute percent error between experimental and accepted values for lab and measurement checks. Interactive calculations run locally; shared URLs and REST use the same engine. Free — no sign-up.
- Percentage Calculator Calculate percentages, percentage of a number, and “what percent is X of Y” with clear arithmetic steps. Runs locally in your browser. Try it free.
- Percentage Change Calculator Calculate the percentage increase or decrease from an initial value to a final value. You can also solve for the initial or final value. Free online — no sign-up.
- Permutation Combination Calculator Exact P(n,k) and C(n,k) for integers 0 ≤ k ≤ n ≤ 1000. Multiplicative BigInt, local-first. Not the factorial calculator.
- Prime Factorization Calculator Factor n = ∏ p^e and test primality for 1 ≤ n ≤ 10^12. Trial division. One capability, two modes.
- Pythagorean Theorem Calculator Solve a right triangle with a² + b² = c². Enter any two of legs a, b and hypotenuse c to find the third side, plus area and perimeter. Try it free.
- Quadratic Formula Calculator Solve ax² + bx + c = 0 with the quadratic formula. Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Ratio Calculator Simplify ratios and scale quantities that stay in proportion. Runs locally in your browser. Free online tool — no sign-up. No account needed.
- Root Calculator Calculate the principal real nth root ⁿ√a. Fast local calculation with shareable, machine-readable results.
- Scientific Notation Calculator Convert numbers to scientific, E, and engineering notation. Free online tool — no sign-up. Mobile-friendly and privacy-first. Runs locally in your browser.
- Sin Calculator Calculate sin(θ) in degrees or radians. Fast local calculation with shareable, machine-readable results.
- Square Root Calculator Calculate the principal square root √x. Fast local calculation with shareable, machine-readable results.
- Subtraction Calculator Subtract minuend − subtrahend to get the difference. Free online tool — no sign-up. Clear formulas and worked examples. Interactive calculations run locally in your browser.
- Sum Calculator Add a list of numbers (sum), see the mean, or work long addition with place-value steps. Paste values separated by commas, spaces, or new lines — decimals and negatives.
- Tan Calculator Calculate tan(θ) = sin(θ)/cos(θ) in degrees or radians. Fast local calculation with shareable, machine-readable results.
- Triangle Solver Solve a Euclidean triangle from SSS, SAS, ASA, AAS, or SSA (ambiguous case). Not the Pythagorean-only calculator. Runs locally.
Wire calculators
Wire gauge, AWG/SWG, and voltage drop.
- AWG to mm Calculator Convert American Wire Gauge (AWG) to conductor diameter in mm and cross-section in mm² with standard AWG tables. Runs locally in your browser.
- SWG to mm Calculator Convert Standard Wire Gauge (SWG) to millimetres and mm² for British/imperial wire sizing. Runs locally in your browser. Free online tool — no sign-up.
- Voltage Drop Calculator Estimate DC or resistive single-phase / balanced three-phase voltage drop and conductor I²R loss from current, cable length, and Ω/km. Optional system voltage shows % drop and load voltage. Runs locally in your browser. Try it free.
- Wire Gauge Chart Look up AWG wire gauge charts for diameter, area, and typical ampacity reference values in one place. Runs locally in your browser. Try it free.
Electrical calculators
Amps, volts, watts, kVA, and power tools.
- 555 Timer Calculator Astable frequency, period, high/low times and duty — or monostable pulse width — for the classic 555 timer from R and C. ln(2)-canonical NE555 timing with device-applicability warnings.
- AC to DC Rectifier Calculator Ideal half-wave/full-wave rectified waveform — peak, average and RMS voltage, with optional capacitor ripple estimation. Runs locally in your browser.
- ADC Error Budget Calculator Combine ADC gain, offset, INL, and DNL errors (RSS or worst-case) into total LSB, volts, and %FS. Runs locally in your browser.
- ADC SNR / Quantization Calculator Ideal quantization SNR ≈ 6.02·N + 1.76 dB for a full-scale sine; reverse measured SINAD to ENOB. Runs locally in your browser.
- Amps to kW Calculator Convert amps and volts to real power in kW for DC, AC single-phase, and balanced AC three-phase line-to-line. Runs locally in your browser. Free online tool — no sign-up.
- Amps to VA Calculator Convert amps and volts to apparent power in VA or kVA for single-phase and three-phase circuits. Also convert VA back to amps. Fast and free.
- Amps to Volts Calculator Solve voltage from current and resistance or power using Ohm’s law and P = V × I. Supports resistive DC and RMS AC estimates with clear formulas.
- Antenna Length Calculator Compute dipole (λ/2) or monopole (λ/4) antenna length from frequency and an empirical length factor. Runs locally in your browser.
- Battery Pack Sizing Calculator Size battery capacity (Ah) from load and runtime targets, with optional series/parallel cell geometry. Inverse of Battery Runtime (watts load-side / amps battery-side).
- Battery Runtime Calculator Estimate battery runtime from capacity (Ah or mAh), voltage, and constant load in watts (load-side) or amps (battery-side), with planning DoD and load-side efficiency. Runs locally in your browser.
- Battery Runtime with Temperature Estimate constant-load battery runtime with a generic cold-derating heuristic about 25 °C. Extends Battery Runtime (watts load-side / amps battery-side). Planning model — not chemistry.
- Buck Converter Ripple Calculator Assumed-CCM buck peak-to-peak inductor ripple ΔI_L,pp = Vout(1−D)/(f L) and optional capacitor-only ΔV_C,pp ≈ ΔI/(8fC). Runs locally in your browser.
- Capacitance Calculator Compute parallel-plate capacitance C=εA/d or combine series/parallel capacitors. Runs locally in your browser.
- Cascaded Noise Figure Calculator Compute cascaded noise figure and total gain for a multi-stage RF chain using the Friis formula. Add, remove, or reorder stages. Runs locally in your browser.
- Coax Impedance Calculator Compute coaxial characteristic impedance Z0 from shield inner diameter D, center-conductor diameter d, and dielectric εr. Ideal TEM, μr≈1. Runs locally in your browser.
- Current Divider Calculator Split a total current between two parallel resistors: I1 = It·R2/(R1+R2), I2 = It·R1/(R1+R2). Runs locally in your browser.
- dBm to Watts Calculator Convert dBm ↔ watts and dBm ↔ milliwatts with hard validation. Canonical Unit Engine for RF power.
- Diode Equation Calculator Shockley diode law I_D=I_S·(e^(V_D/(n·V_T))−1). Solve current or voltage, including reverse branch I_D > −I_S. Runs locally in your browser.
- Electric Power Calculator Calculate electrical power in watts from voltage and current for DC, single-phase AC, or balanced three-phase AC, from current and resistance, or from energy over time.
- Electricity Bill Calculator Estimate an electricity bill from kWh usage or meter readings, with rate, standing charge, and days of service. Runs locally in your browser.
- Energy Consumption Calculator Estimate energy use in kWh from device watts and hours of operation. Useful for appliance and load planning. Runs locally in your browser. Try it free.
- Energy Cost Calculator Estimate electricity usage cost from watts/hours or kWh and your unit rate. Supports custom billing periods; standing charges and taxes are excluded. Runs locally in your browser.
- eV to Volts Calculator Relate electronvolt energy to electric potential difference through ΔE = qΔV. eV and volts measure different physical quantities. Runs locally in your browser.
- Free-Space Path Loss Calculator Compute free-space path loss FSPL = 20·log10(d·f) + 20·log10(4π/c) from distance and frequency, with optional antenna gains. Runs locally in your browser.
- Heatsink Thermal Resistance Calculator — θJC, θCS, θSA & Junction Temperature Size required heatsink θSA from Tj,max, or compute junction temperature from effective θJA or the θJC+θCS+θSA stack. Device dissipation only. Runs locally in your browser.
- High-Pass Filter Calculator First-order RC high-pass cutoff fc=1/(2πRC) and optional |H(f)|. Twin of the LPF calculator.
- Kirchhoff's Law Calculator Apply Kirchhoff’s voltage law to a series loop or current law to a parallel node with N resistors.
- kVA to Amps Calculator Convert kVA and voltage to line current for single-phase and three-phase systems. Uses √3 for three-phase line-to-line volts. Runs locally in your browser.
- kVA to kW Calculator Convert apparent power (kVA) to real power (kW) with power factor. States when PF is required and when loads are assumed balanced. Try it free.
- kW to VA Calculator Convert kilowatts to volt-amperes using power factor. Distinguishes real vs apparent power for feeder and transformer sizing. Runs locally in your browser.
- kWh to kW Calculator Convert kilowatt-hours and duration into average kilowatts. Clarifies energy vs power for metering and solar sizing. Runs locally in your browser.
- kWh to Watts Calculator Convert energy in kWh and a time period into average power in watts (and reverse) for load and generation estimates. Runs locally in your browser.
- L-section LC Match Calculator Narrowband real RL→Z0 L-section match with dual LP/HP solutions. Runs locally in your browser.
- LDO Thermal Calculator Compute LDO dissipation P=(Vin−Vout)·Iout (+ Iq·Vin) and junction temperature. Runs locally in your browser.
- LED Resistor Calculator Size the series resistor for one or more LEDs: R = (Vs − n·Vf) / If.
- Linear Battery Aging Calculator Estimate battery capacity with a simple linear cycle + calendar aging model: SOH = max(0, 1 − k_cycle·N − k_cal·t), C = C0·SOH. Default coefficients are illustrative. Runs locally in your browser.
- Logic Gate Calculator Evaluate basic digital logic gates from binary inputs. Runs locally in your browser.
- Low-Pass Filter Calculator Design a first-order RC low-pass filter: solve any two of R, C, and cutoff fc = 1/(2πRC), and evaluate magnitude |H(f)| in linear and dB. Runs locally in your browser.
- mAh to Wh Calculator Convert battery capacity from mAh to Wh (and reverse) using nominal voltage—common for USB power banks and Li-ion packs. Runs locally in your browser.
- Microstrip Impedance Calculator Compute microstrip characteristic impedance Z0 from W/H/εr, or synthesize width for a target Z0 (zero-thickness IPC-2141 / Wadell–Hammerstad). Runs locally in your browser.
- MOSFET Conduction Loss Calculator Calculate MOSFET conduction loss from I, Rds(on), current definition (DC / on-interval RMS / full-cycle RMS), and optional Rds(Tj) via linear α or datasheet ratio. Runs locally in your browser.
- MOSFET Junction Temperature Calculator Estimate MOSFET junction temperature from ambient, dissipation, and thermal resistance (effective RθJA, or case/heatsink-dominant RθJC+RθCA). Optional thermal margin.
- MOSFET Switching Loss Calculator First-order hard-switching overlap loss P_sw = ½·Vds·Id·(tr+tf)·f_sw, plus optional gate-drive power Qg·Vdrive·f. Not a full MOSFET loss stack. Runs locally in your browser.
- MOSFET Threshold & Overdrive Calculator Calculate MOSFET overdrive Vod=Vgs−Vth, square-law drain current, or model Vth. Vth here is the long-channel square-law parameter — not datasheet VGS(th). Runs locally in your browser.
- MOSFET Total Loss Calculator MOSFET device dissipation from conduction + hard-switching + optional Coss/Eoss, plus optional gate-drive and Qrr commutation. Tj uses P_device, not associated total. Omitted terms are not treated as 0 W. Runs locally in your browser.
- Ohm's Law Calculator Enter any two of voltage, current, resistance, and power to solve the remaining values. Runs locally in your browser. Free online tool — no sign-up.
- Op-amp Error Budget Calculator Estimate DC output-referred error from Vos, Ib, Ios and feedback resistors (RSS or worst-case).
- Op-Amp Gain Calculator Closed-loop gain for non-inverting (1+Rf/Rg) and inverting (−Rf/Rg) op-amp circuits. Runs locally in your browser.
- Op-amp Noise Calculator Estimate flat-band output noise from en, optional in, gain, and bandwidth. Runs locally in your browser.
- Parallel Resistor Calculator Compute equivalent resistance of two or more resistors in parallel. Runs locally in your browser.
- PCB Differential Impedance Calculator Estimate edge-coupled microstrip differential impedance Zdiff from W, H, S, and εr. Hammerstad/Wadell Z0 plus IPC-2141A-style coupling. Runs locally in your browser.
- PCB Trace Thermal Calculator Estimate copper trace I²R power and temperature rise with a board thermal resistance. Runs locally in your browser.
- PCB Trace Width Calculator (IPC-2221) Size PCB copper traces from current and temperature rise using the classic IPC-2221 I = k·ΔT^0.44·A^0.725 relation for external and internal layers. Runs locally in your browser.
- Power Factor Calculator Calculate power factor from real power, voltage, and current for single-phase and three-phase (line-line or line-neutral) circuits. Try it free.
- RC Time Constant Calculator Calculate the RC time constant τ = R×C, solve for R or C, and get −3 dB frequency plus 2.2τ / 5τ timing estimates. Runs locally in your browser.
- Receiver Sensitivity Calculator Estimate MDS: S = −174 + NF + 10·log10(BW) + SNR_min (dBm). Runs locally in your browser.
- Rectifier Ripple Capacitor Calculator Size filter capacitance or estimate ripple for half/full-wave rectifiers: Vripple ≈ I/(f·C). Runs locally in your browser.
- Reflection Coefficient to Impedance Calculator Convert complex Γ ↔ normalized z (Cartesian or polar Γ). Reports VSWR and return loss. Runs locally in your browser.
- Resistor Color Code Calculator IEC 60062 band colors → Ω ±tol. Runs locally in your browser.
- RF Link Budget Calculator Compute RF link budget: FSPL, path loss with antenna gains and misc loss, received power, and optional margin above sensitivity. Extends Free-Space Path Loss.
- RLC Resonance Calculator Calculate RLC resonant frequency f₀, Q factor, bandwidth, and reactance at resonance for series or parallel circuits from L, C, and R. Runs locally in your browser.
- Series Capacitor Calculator Combine capacitors in series: 1/C = Σ 1/Ci. Runs locally in your browser.
- Skin Depth Calculator Compute electromagnetic skin depth δ = √(ρ/(π·f·μ)) for conductors. Runs locally in your browser.
- Smith Chart Calculator Interactive impedance Smith chart with auto-match, drag-to-tune, L·C·R / T-line / stub / transformer / ‖RLC, Custom Z(f), f-locus, and Touchstone S11/S21 with stability overlays. Runs locally in your browser.
- Stripline Impedance Calculator Estimate symmetric stripline characteristic impedance from W, b, and εr. Extends microstrip / Zdiff. Runs locally in your browser.
- Transformer Sizing Calculator Ideal transformer: Vp/Vs=Np/Ns, currents, and VA = V·I. First-pass sizing. Runs locally in your browser.
- VA to kVA Calculator Convert volt-amperes (VA) to kilovolt-amperes (kVA) with the exact 1000× scale factor used on nameplates. Runs locally in your browser. Try it free.
- Via Current Capacity Calculator Estimate PCB via ampacity from drill diameter, plating thickness, and temperature rise using the IPC-2221 I = k·ΔT^0.44·A^0.725 relation on the plating cross-section.
- Voltage Divider Calculator Solve a two-resistor voltage divider: enter exactly three of Vin, R1, R2, and Vout to find the fourth. Also reports current, power, ratio, and Rth. Try it free.
- Volts to Joules Calculator Relate voltage, charge, or capacitance to energy in joules for electrostatic and capacitor examples. Runs locally in your browser. Try it free.
- Volts to kW Calculator Estimate kilowatts from voltage, current, and power factor for single-phase and three-phase circuits. Runs locally in your browser. Try it free.
- VSWR Calculator Convert between reflection coefficient |Γ|, VSWR, and return loss. Runs locally in your browser.
- Watts to Amps Calculator Convert watts to amps (and reverse) for DC, single-phase, and three-phase circuits. Power factor and voltage inputs included for AC loads. Try it free.
- Watts to Joules Calculator Convert watts and time to energy in joules (and reverse). Shows W × s = J with worked timing examples. Runs locally in your browser. Try it free.
- Watts to kVA Calculator Convert watts to kVA with power factor. Helps size generators and UPS equipment from real power demand. Runs locally in your browser. Try it free.
- Watts to VA Calculator Convert real power in watts to apparent power in VA using power factor. Clarifies W vs VA for sizing breakers and transformers. Try it free.
- Watts to Volts Calculator Find voltage from power and current (or resistance). Useful for DC and resistive AC checks with unit guidance. Runs locally in your browser.
- Watts Volts Amps Calculator Solve any two of watts, volts, amps, and ohms for the other values—an Ohm’s-law style watt–volt–amp workspace. Runs locally in your browser.
- Wavelength Calculator Compute λ = c·VF/f in vacuum or dielectric. Solve for wavelength or frequency. Runs locally in your browser.
- Wheatstone Bridge Calculator Compute Wheatstone bridge output voltage and balance from Vin and four resistors. Runs locally in your browser.
Physics calculators
Mechanics, energy, thermodynamics, waves, and optics.
- Acceleration Calculator Solve constant acceleration a=(v−u)/t. Runs locally in your browser.
- Bernoulli Equation Calculator Incompressible Bernoulli along a streamline: solve P2, v2, or h2. Runs locally in your browser.
- Binary to Hex Converter Convert unsigned integers between binary and hexadecimal. Runs locally in your browser.
- Boyle's Law Calculator P₁V₁ = P₂V₂. Runs locally in your browser.
- Cavitation Number Calculator Compute the cavitation number σ = (p − p_v) / (½ ρ v²). Runs locally. Not NPSH, not Thoma NPSH/H, not Weber, and not Euler Eu=Δp/(ρ v²).
- Celsius to Kelvin Converter Convert between Celsius and Kelvin with hard absolute-zero checks. Runs locally in your browser.
- Centripetal Force Calculator F = m v² / r. Runs locally in your browser.
- Charles's Law Calculator V₁/T₁ = V₂/T₂. Runs locally in your browser.
- Chezy Formula Calculator Compute open-channel mean velocity V = C √(R S). Runs locally. Not Manning n, not Q=Av, not Hazen–Williams, and not Darcy.
- Colebrook Friction Factor Calculator Solve the Colebrook–White equation for Darcy friction factor f from Re and ε/D. Turbulent pipes Re≥4000. Runs locally. Not laminar 64/Re and not a Moody-chart lookup.
- Composite Wall Calculator Compute plane composite-wall resistance from a layer list. R_i = L_i/(k_i A), optional films 1/(h A), R = R_in + ΣR_i + R_out. Optional Q=ΔT/R. Runs locally. Not Fourier/Newton Q, not a lumped R-network, and not heatsink θ.
- Concentric Reducer Calculator Compute concentric-reducer loss h = K v₂² / (2g) with K = 0.5 (1 − A₂/A₁) referenced to the downstream speed. Runs locally. Not sudden expansion, not gradual contraction α, not vena-contracta C_c, not catalog K, and not Q=Av.
- Coulomb's Law Calculator Compute electrostatic force F = k·|q1·q2|/r² between point charges. Runs locally in your browser.
- Critical Depth Calculator Compute rectangular critical depth yc = (q²/g)^{1/3}. Runs locally. Not a Froude wrap, not specific energy, not a hydraulic jump, and not Q=Av.
- Darcy–Weisbach Calculator Compute pipe head loss hf = f L v²/(2 g D) and Δp = ρ g hf from a given Darcy friction factor. Runs locally. Does not solve Colebrook for f.
- Displacement Calculator Δx = x − x₀. Runs locally in your browser.
- Doppler Effect Calculator f' = f (v±vo)/(v±vs). Runs locally in your browser.
- Drag Force Calculator Fd = ½ ρ v² Cd A. Runs locally in your browser.
- Efficiency Calculator Power efficiency η=Pout/Pin as fraction and percent. Runs locally in your browser.
- Electric Field Calculator E = k|Q|/r². Runs locally in your browser.
- Faraday's Law Calculator ε = N |ΔΦ| / Δt. Runs locally in your browser.
- Flow Rate Calculator Volumetric flow Q=A·v (or from pipe diameter). Runs locally in your browser.
- Force Calculator (F=ma) Solve Newton’s second law for force, mass, or acceleration. Runs locally in your browser.
- Free Fall Calculator Free-fall distance, speed, or time under constant g (optional initial velocity). Runs locally in your browser.
- Friction Calculator F = μ N. Runs locally in your browser.
- Froude Number Calculator Compute the open-channel Froude number Fr = v / √(g L). Default g=9.80665 m/s². Runs locally. Not Reynolds, not Manning, not Chezy, and not Q=Av.
- Gradual Contraction Calculator Compute conical-contraction loss h = K v2² / (2g) with K = 0.5 sin(α) (1 − v1/v2). α is the wall half-angle. Runs locally. Not sudden contraction, not gradual expansion, not minor-loss K as an input, and not Q=Av.
- Gradual Expansion Calculator Compute conical-diffuser loss h = k (v1 − v2)² / (2g) with k = 2.6 sin(α). α is the wall half-angle. Runs locally. Not sudden expansion, not minor-loss K as an input, and not Q=Av.
- Hagen–Poiseuille Calculator Compute laminar circular-pipe flow Q = π Δp D⁴ / (128 μ L). Runs locally. Not Darcy f, not Colebrook, and not Q=Av.
- Half-Life Calculator Radioactive decay with N=N₀·2^(−t/T½). Runs locally in your browser.
- Hazen–Williams Calculator Compute SI Hazen–Williams head loss hf = 10.67 L Q^{1.852} / (C^{1.852} D^{4.87}) for a circular water pipe. Runs locally. Not Darcy–Weisbach, not Colebrook, and not Manning.
- Heat Transfer Calculator Compute conductive Q=kAΔT/L or convective Q=hAΔT heat transfer rate. Runs locally in your browser.
- Hydraulic Diameter Calculator Compute hydraulic diameter D_h=4A/P_w for a general section, a full circular pipe, a closed rectangular duct, or an annulus. Runs locally. Not Q=Av, not Manning, and not Darcy.
- Hydraulic Jump Calculator Compute rectangular sequent depths y₂/y₁ = (√(1+8 Fr₁²) − 1)/2. Fr₁ > 1. Runs locally. Not a Froude wrap, not Manning, not a weir, and not Q=Av.
- Hz to Rad/s Converter Convert between hertz and radians per second with ω = 2πf. Runs locally in your browser.
- Ideal Gas Law Calculator Solve the ideal gas law for P, V, n, or T with SI units. Runs locally in your browser.
- Impulse Calculator J = F Δt = Δp. Runs locally in your browser.
- ISO 5167 Nozzle Calculator Compute ISO 5167-3 ISA 1932 nozzle discharge with C from β and Re_D, not a given C_d. Runs locally. Not a venturi wrap with C_d=0.98, not orifice C_d=0.61, not Q=Av, and not Darcy.
- Joule to eV Converter Convert energy between joules and electronvolts (exact SI factor). Runs locally in your browser.
- Kinetic Energy Calculator KE = ½ m v². Runs locally in your browser.
- kWh to Joules Converter Convert energy between kilowatt-hours and joules (1 kWh = 3.6 MJ). Runs locally in your browser.
- Lens Maker Calculator 1/f = (n−1)(1/R1 − 1/R2). Runs locally in your browser.
- m/s to km/h Converter Convert speed between metres per second and kilometres per hour (×3.6). Runs locally in your browser.
- Magnetic Field Calculator B = μ₀ I / (2π r). Runs locally in your browser.
- Manning Formula Calculator Compute SI Manning discharge Q = (1/n) A R^{2/3} S^{1/2}. Runs locally. Not Q=Av, not Darcy–Weisbach, and not a weir.
- Minor Loss Calculator Compute fitting minor loss h_m = K v²/(2g). Optional Δp = ρ g h_m. Runs locally. Not Darcy–Weisbach, not Hazen–Williams, and not an orifice.
- Mitered Bend Calculator Compute sharp mitered-elbow loss h = K v² / (2g) with K = n [sin²(δ/2) + 2 sin⁴(δ/2)], δ = θ/n. Runs locally. Not circular-arc R/D, not minor-loss K as an input, not Crane f_T, and not Q=Av.
- Momentum Calculator Solve linear momentum p=mv for p, m, or v. Runs locally in your browser.
- Newton to Lbf Converter Convert force between newtons and pound-force (1 lbf = 4.4482216152605 N). Runs locally in your browser.
- NPSH Calculator Compute NPSH available from an open tank or a suction flange, and compare with manufacturer NPSHr. Runs locally. Not pump power, not an orifice, not a weir, not Q=Av, and not Darcy.
- Orifice Discharge Calculator Compute sharp-edged orifice discharge. Tank Q=C_d A √(2gH). Meter Q=C_d E A_t √(2Δp/ρ) with E=1/√(1−β⁴). Runs locally. Not a weir, not Q=Av, not Darcy, and not Manning.
- Pipe Bend Calculator Compute circular-arc bend loss h = K v² / (2g) with K = 0.21 (θ/90)/√(R/D). Runs locally. Not minor-loss K as an input, not mitered, not Darcy, and not Q=Av.
- Pipe Cross Calculator Compute equal-area sharp 90° four-way cross loss h = K v_c² / (2g) from dividing or combining flow and branch or through split with equal opposite laterals. Runs locally. Not a 90° tee, not a wye, not catalog K, and not Q=Av.
- Pipe Entrance Calculator Compute pipe-inlet loss h = K v² / (2g) from geometry: flush K=0.5, reentrant K=0.8, rounded K=0.5/[1+36(rᵢ/D)^1.2]. Runs locally. Not catalog K, not circular-arc R/D, not mitered n, and not Q=Av.
- Pipe Exit Calculator Compute pipe-exit loss h = K v² / (2g) with K=1 into a large reservoir. Runs locally. Not catalog K, not inlet geometry, not sudden expansion (v1−v2)², and not Q=Av.
- Pipe Period Calculator Compute the water-hammer pipe period T = 2L/c. Runs locally. Not Joukowsky Δp, not Korteweg–Hall c from K/D/e/E, and not Darcy f.
- Pipe Tee Calculator Compute equal-area sharp 90° T loss h = K v_c² / (2g) from dividing or combining flow and branch or run split. Runs locally. Not catalog K, not a bend, not pipe-entrance, not pipe-exit, and not Q=Av.
- Pipe Wye Calculator Compute equal-area sharp wye loss h = K v_c² / (2g) from branch angle α in (0, 90°), dividing or combining flow, and branch or run split. Runs locally. Not a 90° tee, not catalog K, not a bend, and not Q=Av.
- Pitot Tube Calculator Compute incompressible pitot-static speed v = C √(2 Δp / ρ). Default C=1. Runs locally. Not a venturi, not an orifice, not Q=Av, and not two-station Bernoulli.
- Potential Energy Calculator PE = m g h. Runs locally in your browser.
- Projectile Motion Calculator Compute range, apex height, and flight time for flat-ground projectile motion (no drag). Runs locally in your browser.
- Projectile Trajectory Calculator R = v₀² sin(2θ) / g. Runs locally in your browser.
- PSI to Bar Converter Convert between pound-force per square inch and bar. Runs locally in your browser.
- Pump Power Calculator Compute incompressible pump power P=ρgQH/η and affinity-law scaling Q∝ND, H∝N²D², P∝N³D³. Runs locally. Not an orifice, not a weir, not Q=Av, and not Darcy.
- Reynolds Number Calculator Compute Re = ρvL/μ (or vL/ν) with laminar/turbulent guidance for pipes. Runs locally in your browser.
- Snell's Law Calculator n₁ sinθ₁ = n₂ sinθ₂. Runs locally in your browser.
- Sound Level Calculator L = 10 log₁₀(I/I₀). Runs locally in your browser.
- Specific Energy Calculator Compute open-channel specific energy E = y + v²/(2g). Runs locally. Not a Froude wrap, not a hydraulic jump, and not Q=Av.
- Specific Heat Capacity Calculator Solve Q = m c ΔT for heat, mass, specific heat, or temperature change. Runs locally in your browser.
- Stefan–Boltzmann Calculator Compute net gray-body flux q = εσ(Th⁴−Tc⁴) and optional Q = A·q. σ from CODATA 2018. Runs locally. Not Fourier/Newton heat-transfer and not a view-factor solver.
- Sudden Contraction Calculator Compute vena-contracta sudden-contraction loss h = (1/C_c − 1)² v2² / (2g). Default C_c=0.62. Runs locally. Not sudden expansion, not minor-loss K as an input, not an orifice, and not Q=Av.
- Sudden Expansion Calculator Compute Borda–Carnot sudden-expansion loss h = (v1 − v2)² / (2g). Runs locally. Not minor-loss K as an input, not Darcy, not an orifice, and not Q=Av.
- SUVAT Calculator Constant-acceleration kinematics: solve v, s, a, or t (SUVAT). Runs locally in your browser.
- Tesla to Gauss Converter Convert magnetic flux density between tesla and gauss (1 T = 10000 G). Runs locally in your browser.
- Thermal Resistance Calculator Compute lumped thermal resistance. Conduction R=L/(k A), convection R=1/(h A), series ΣR, parallel 1/R=Σ1/R_i. Optional Q=ΔT/R. Runs locally. Not Fourier/Newton Q, not heatsink θ, and not steam.
- Time Dilation Calculator Δt = γ Δτ. Runs locally in your browser.
- Torque Calculator Compute torque τ = r F sinθ. Runs locally in your browser.
- Valve Flow Coefficient Calculator Compute incompressible liquid valve flow from Kv or Cv. Q_m³/h = Kv √(Δp_bar/SG). Kv = 0.865 Cv. Runs locally. Not a venturi, not an orifice, not Q=Av, and not Darcy.
- Velocity Calculator Solve average velocity v=s/t for v, s, or t. Runs locally in your browser.
- Venturi Meter Calculator Compute incompressible venturi flow Q = C_d A2 √(2Δp/(ρ(1−β⁴))) with β = D2/D1. Default C_d = 0.98. Runs locally. Not an orifice plate, not Q=Av, not Darcy, and not valve Cv/Kv.
- Viscosity Calculator τ = η du/dy. Runs locally in your browser.
- Water Hammer Calculator Compute Joukowsky water-hammer Δp = ρ c Δv. Runs locally. Not Darcy f, not minor-loss K, and not Q=Av.
- Watts to Horsepower Converter Convert power between watts and mechanical horsepower (1 hp = 745.6998715822702 W). Runs locally in your browser.
- Wave Celerity Calculator Compute pipe-wave celerity c = √[(K/ρ)/(1+(K D)/(E e))]. Runs locally. Not Joukowsky Δp, not Darcy f, and not minor-loss K.
- Weber Number Calculator Compute the Weber number We = ρ v² L / σ. Runs locally. Not Reynolds, not Froude, not Manning, not Q=Av, and not capillary Ca=μv/σ.
- Weir Discharge Calculator Compute thin-plate weir discharge. Rectangular Q=(2/3) C_d L √(2g) H^{3/2}. V-notch Q=(8/15) C_d √(2g) tan(θ/2) H^{5/2}. Runs locally. Not Manning, not Q=Av, not Darcy, and not an orifice.
- Work and Power Calculator Compute work W=Fs cosθ and power P=W/t or Fv. Runs locally in your browser.
- Young's Modulus Calculator Y = (F/A) / (ΔL/L₀). Runs locally in your browser.
Chemistry calculators
Amount of substance, solutions, and acid-base pH.
- Henderson–Hasselbalch Calculator Compute buffer pH = pKa + log10([A−]/[HA]). Accepts pKa or Ka. Runs locally. Not ICE equilibrium and not pH = −log10[H+].
- Molarity Calculator Compute molarity c = n/V and dilution C1·V1 = C2·V2. Runs locally. Not mole n=m/M and not Henderson–Hasselbalch.
- Mole Calculator Compute amount n = m/M and particle count N = n·N_A. N_A is CODATA 2018 exact. Runs locally. Not molarity and not Henderson–Hasselbalch.
- pH Calculator Compute pH = −log10[H+] and pOH = −log10[OH−] at 25 °C with Kw = 1e-14. Runs locally. Not Henderson–Hasselbalch and not ICE.
- Weak-Acid Equilibrium Calculator Solve monoprotic weak-acid ICE from formal C and Ka or pKa. Charge and mass balance; optional water at 25 °C. Runs locally. Not Henderson–Hasselbalch and not pH = −log10[H+] identities.
- Weak-Base Equilibrium Calculator Solve monoprotic weak-base ICE from formal C and Kb or pKb. Charge and mass balance; optional water at 25 °C. Runs locally. Not Henderson–Hasselbalch and not weak-acid ICE.
Engineering calculators
Tolerance, uncertainty, and engineering analysis tools.
- Cochran's C Calculator Compute ISO 5725-2 Cochran's C from k≥2 stated laboratory sample standard deviations. Runs locally. Not pooled s_p, not Hartley's F_max, and not a tabulated Ccrit pass/fail.
- Conformity Decision Rule Calculator Apply a binary ILAC G8-style decision to a measured value y: simple acceptance (w=0) or guarded acceptance (LSL+w ≤ y ≤ USL−w). Runs locally. Not JCGM 106 risk tables and not TUR.
- Coverage Factor Calculator Compute the two-sided Student-t coverage factor k from degrees of freedom ν and confidence p. Infinite ν uses the normal quantile. Runs locally. Not expanded U = k·u_c.
- Gauge Capability Calculator (Cg / Cgk) Compute Type-1 Cg and Cgk from repeats on a master, a reference xm, and the characteristic tolerance. frac defaults to 0.2. Runs locally. Not AIAG GRR and not process Cp/Cpk.
- Gauge R&R Calculator Compose AIAG Gauge R&R from EV, AV, and PV: GRR, TV, %GRR, and ndc. Optional range-method EV = R̄/d2. Runs locally. Not a full ANOVA study.
- Guard Band Calculator Compute a simple guard band GB=k·u and optional acceptance limits USL−GB and LSL+GB. Runs locally. Not ILAC G8 risk-based decision rules.
- Inverse-Variance Weighted Mean Calculator Combine independent results of the same measurand with the GUM H.3 inverse-variance weighted mean. Runs locally. Not combined RSS, not Type A u_A, and not GUM propagate.
- ISO 5725 Reproducibility Calculator Compute the ISO 5725 reproducibility limit from stated components s_r and s_L: s_R = √(s_r²+s_L²), R = 2.8·s_R. Runs locally. Not r from a sample, not AIAG GRR, and not combined RSS.
- Maximum Permissible Error Calculator Decide whether a measured value meets the VIM maximum permissible measurement error: pass iff |ylab−xref| ≤ MPE. Runs locally. Not an ILAC G8 spec decision, not En, and not ε-only.
- Measurement Bias Calculator Compute VIM trueness as the signed bias = x̄ − xm from repeats on a master. Runs locally. Not a single-shot measurement error, not Type A u_A, and not Cg.
- Measurement Error Calculator Compute the VIM signed measurement error ε = ylab − xref and the relative error ε/xref. Runs locally. Not percent error, not En, and not a z-score.
- Measurement Precision Calculator Compute ISO 5725 repeatability from a sample: s, CV = s/|x̄|, and r = 2.8·s. Runs locally. Not Type A u_A, not Gauge R&R EV, and not percent CV.
- Monte Carlo Tolerance Calculator 1-D Tolerance Analysis Workspace: dimensional Monte Carlo with asymmetric ±tol, correlations, sensitivity ranking, σ convergence, LSL/USL yield, simulated capability, and immutable Freeze snapshots.
- MSA Hysteresis Calculator Compute VIM / MSA hysteresis as the maximum absolute difference between increasing and decreasing indications at index-paired stations. Runs locally. Not OLS linearity, not a %Hysteresis pass/fail, and not Gauge R&R.
- MSA Linearity Calculator Fit ordinary least squares of measurement error ε = ylab − xref versus xref. Reports slope, intercept, and r². Runs locally. Not a single-master bias, not Type-1 Cg, and not a %Linearity pass/fail.
- Normalized Error Calculator Compute the proficiency-testing normalized error En from a laboratory result, a reference value, and two already-expanded uncertainties. |En| ≤ 1 is pass. Runs locally. Not zeta, not TUR, and not an ILAC G8 spec decision.
- Pooled Standard Deviation Calculator Compute a pooled standard deviation from k≥2 stated sample s_i and their degrees of freedom ν_i. Runs locally. Not Type A from one sample, not Welch–Satterthwaite ν_eff, and not ISO 21748 u of a mean.
- Process Capability Calculator (Cp / Cpk) Compute design-stage Cp, Cpk, Cpu, and Cpl from process mean, σ, LSL, and USL. Runs locally in your browser. Not Monte Carlo simulated capability.
- Process Capability Cpm Calculator Compute Taguchi Cpm from μ, σ, LSL, USL, and a target. Runs locally. Not Cp/Cpk, not Pp/Ppk, and not a 1.33 verdict.
- Process Capability Cpmk Calculator Compute Taguchi Cpmk from μ, σ, LSL, USL, and a target. Runs locally. Not Cpm, not Cpk, not Ppm, and not a 1.33 verdict.
- Process Performance Calculator (Pp / Ppk) Compute overall Pp, Ppk, Ppu, and Ppl from process observations, LSL, and USL. σ is the overall sample s. Runs locally. Not design-stage Cp/Cpk and not Type A u_A.
- Process Performance Ppm Calculator Compute overall Taguchi Ppm from observations, LSL, USL, and a target. Runs locally. Not design-stage Cpm, not Pp/Ppk, and not a 1.33 verdict.
- Process Performance Ppmk Calculator Compute overall Taguchi Ppmk from observations, LSL, USL, and a target. Runs locally. Not Cpmk, not Ppk, not Ppm, and not a 1.33 verdict.
- Proficiency-Testing z-Score Calculator Compute the ISO 13528 proficiency-testing z-score from a laboratory result, an assigned value, and the scheme SDPA σ_pt. |z| ≤ 2 is pass. Runs locally. Not zeta, not En, and not an ILAC G8 spec decision.
- Proficiency-Testing z′ Calculator Compute the ISO 13528 z′ score from a laboratory result, an assigned value, the scheme SDPA σ_pt, and the standard uncertainty of that assigned value. |z′| ≤ 2 is pass. Runs locally. Not z-score, not zeta, and not En.
- Repeatability from Duplicates Calculator Compute ISO 5725 repeatability s_r from m≥2 duplicate differences. Runs locally. Not Type A from a sample of observations, not r = 2.8·s, and not AIAG GRR EV = R̄/d2.
- Test Uncertainty Ratio Calculator Compute the two-sided test uncertainty ratio TUR from an already-expanded U and a specification interval. Runs locally. Not a pass/fail, not a guard band, and not combined RSS.
- Tolerance Stack-up Calculator Combine dimensional tolerances with worst-case sum or RSS root-sum-square. Basic magnitude list or Engineering mode with nominal, ±tol, and direction.
- Type A Uncertainty Calculator Compute Type A standard uncertainty from repeated observations: mean, sample s, and u_A = s/√n. Runs locally. Not GUM combination and not Monte Carlo.
- Type B Degrees of Freedom Calculator Compute GUM G.4.2 Type B degrees of freedom from a stated standard uncertainty u and its standard uncertainty σ(u). σ(u)=0 → ν is infinite. Runs locally. Not Type B u_B, not Welch ν_eff, and not U = k·u_c.
- Type B Uncertainty Calculator Compute Type B standard uncertainty from a half-width a. Rectangular u_B = a/√3, triangular u_B = a/√6. Runs locally. Not GUM combination and not Monte Carlo.
- Uncertainty of a Mean from Precision Calculator Compute the ISO 21748 standard uncertainty of a mean of n≥2 replicates from stated precision components s_r and s_L. Runs locally. Not R = 2.8·s_R, not Type A from a sample, and not U = k·u.
- Uncertainty Propagation Calculator Propagate measurement uncertainty using GUM linear propagation, covariance, uncertainty budgets, or Monte Carlo simulation. Optional correlation ρ and coverage factor k → U. Runs locally in your browser.
- Welch–Satterthwaite Calculator Compute GUM G.4 effective degrees of freedom ν_eff from standard uncertainty components u_i and their ν_i. Runs locally. Not combined RSS and not expanded U = k·u_c.
- Worst-Case Tolerance Analysis Calculator 1-D linear dimensional tolerance stack: worst-case Σ|tol| with RSS comparison. Deterministic bound under declared limits — pairs with Tolerance Stack-up and Monte Carlo.
- Zeta-Score Calculator Compute the proficiency-testing zeta-score from a laboratory result, a reference value, and two standard uncertainties. |ζ| ≤ 2 is pass. Runs locally. Not En, not TUR, and not an ILAC G8 spec decision.
Time calculators
Age, dates, duration, and world clocks.
- Age Calculator Calculate exact age in years, months, and days from a birth date to today or a chosen date. Runs locally in your browser. Free online tool — no sign-up.
- Alaska / Anchorage Time Live local time in Anchorage and most of Alaska (America/Anchorage). See AKST UTC−9, AKDT UTC−8, DST dates, and how Alaska Time compares to other U.S.
- Bangkok / Thailand Time Show current time in Bangkok (Indochina Time, UTC+7) with a simple world-clock style readout. Runs locally in your browser. Free online tool — no sign-up.
- Beijing / China Time Live local time in Beijing and all of mainland China (Asia/Shanghai). China Standard Time (CST) is UTC+8 year-round with no Daylight Saving Time.
- Chicago / Central Time Live local time in Chicago (America/Chicago). See CST UTC−6, CDT UTC−5, U.S. DST dates, and how Central Time compares to Eastern, Mountain, and Pacific.
- Days in a Year How many days in 1 year? Free online tool — no sign-up. Clear formulas and worked examples. Built for quick, accurate checks. Runs locally in your browser.
- Denver Time Live local time in Denver (America/Denver). See MST UTC−7, MDT UTC−6, U.S. DST dates, and how Mountain Time compares to Pacific, Central, and Eastern.
- Hawaii Time Live local time in Honolulu and Hawaii (Pacific/Honolulu). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Hong Kong Time Live local time in Hong Kong (Asia/Hong_Kong). Hong Kong Time is UTC+8 year-round with no Daylight Saving Time. Runs locally in your browser. Try it free.
- Hours in a Week Use the free Hours in a Week on CalculatorX for fast local results. Clear formulas, assumptions, and worked examples on the page. No account needed.
- Hours in a Year Use the free Hours in a Year on CalculatorX for fast local results. Clear formulas, assumptions, and worked examples on the page. No account needed.
- India Time (IST) Live local time in India (Asia/Kolkata). Indian Standard Time is UTC+5:30 year-round with no Daylight Saving Time — one zone for the whole country.
- Los Angeles Time Live local time in Los Angeles (America/Los_Angeles). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Minutes in a Day Use the free Minutes in a Day on CalculatorX for fast local results. Clear formulas, assumptions, and worked examples on the page. Fast and free.
- Months in a Year Use the free Months in a Year on CalculatorX for fast local results. Clear formulas, assumptions, and worked examples on the page. Fast and free.
- Nepal Time Live local time in Kathmandu and Nepal (Asia/Kathmandu). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- New York Time Live local time in New York (America/New_York). See EST UTC−5, EDT UTC−4, U.S. DST dates, and how Eastern Time compares to Central, Mountain, and Pacific.
- Pakistan Time Live local time in Karachi and Pakistan (Asia/Karachi). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Philippines Time Live local time in Manila and the Philippines (Asia/Manila). Free online tool — no sign-up. Built for quick, accurate checks. Runs locally in your browser.
- Phoenix Time Live local time in Phoenix, Arizona (America/Phoenix). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Seconds in a Day Use the free Seconds in a Day on CalculatorX for fast local results. Clear formulas, assumptions, and worked examples on the page. Fast and free.
- Seconds in a Year How many seconds in 1 year (365 d)? Works offline-ready. Free online tool — no sign-up. Runs locally in your browser. Clear formulas and worked examples.
- Seconds in an Hour How many seconds in 1 hour? Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser. Simple and accurate.
- Seoul Time Live local time in Seoul and South Korea (Asia/Seoul). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Singapore Time Live local time in Singapore (Asia/Singapore). Singapore Time is UTC+8 year-round with no Daylight Saving Time. Runs locally in your browser. Try it free.
- Taiwan Time Live local time in Taipei and Taiwan (Asia/Taipei). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Tokyo / Japan Time Live local time in Tokyo and Japan (Asia/Tokyo). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- UK / London Time Live local time in London and the UK (Europe/London). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- UTC Time Live UTC clock (UTC+0). Free online tool — no sign-up. Clear formulas and worked examples. Mobile-friendly and privacy-first. Runs locally in your browser.
- Weeks in a Month Count how many weeks fall in a given calendar month, with options for week-start conventions. Runs locally in your browser. Free online tool — no sign-up.
- Weeks in a Year Use the free Weeks in a Year on CalculatorX for fast local results. Clear formulas, assumptions, and worked examples on the page. No account needed.
Financial calculators
Interest, VAT, GST, and related finance tools.
- Break-Even Calculator Find break-even units or sales from fixed costs, variable cost per unit, and selling price. Runs locally in your browser. Free online tool — no sign-up.
- CAGR Calculator Calculate compound annual growth rate (CAGR) from beginning value, ending value, and years. Runs locally in your browser. Free online tool — no sign-up.
- Compound Interest Calculator Project future value with compound interest from principal, rate, compounding frequency, and time. Optional contributions. Runs locally in your browser.
- Discount Calculator Apply a percent discount to a price and show savings and final amount. Runs locally in your browser. Free online tool — no sign-up. Try it free.
- GST Calculator Add or remove GST from prices at a chosen GST rate for inclusive/exclusive totals. Runs locally in your browser. Free online tool — no sign-up.
- Loan Amortization Calculator Build a loan amortization schedule: payment, interest, principal, and remaining balance by period. Runs locally in your browser. Try it free.
- Loan Payment Calculator Calculate fixed monthly loan payments from principal, annual rate, and term. Shows amortization-style payment math. Runs locally in your browser.
- Markup Calculator Calculate selling price or markup percentage from cost and desired margin. Runs locally in your browser. Free online tool — no sign-up. Try it free.
- Present Value Calculator Discount a future amount to present value at a chosen rate and number of periods. Runs locally in your browser. Free online tool — no sign-up.
- Profit Margin Calculator Compute gross or net profit margin from revenue and cost (or profit). Shows margin vs markup differences. Runs locally in your browser. Try it free.
- ROI Calculator Measure return on investment as gain or loss versus cost, with percentage ROI and net profit. Runs locally in your browser. Free online tool — no sign-up.
- Savings Goal Calculator Estimate deposits needed to reach a savings goal given rate, compounding, and timeline. Runs locally in your browser. Free online tool — no sign-up.
- Simple Interest Calculator Calculate simple interest and total amount from principal, rate, and time—no compounding. Runs locally in your browser. Free online tool — no sign-up.
- VAT Calculator Add or remove VAT from a net or gross price at a chosen VAT rate. Runs locally in your browser. Free online tool — no sign-up. Fast and free.
Lighting calculators
Lumens, lux, candela, and lighting conversions.
- Candela to Lumen Calculator Convert candela (cd) to lumens (lm) using beam angle: lm = cd × 2π(1 − cos(θ/2)). Reverse lumens to candela. Includes solid angle and full-sphere 4π.
- Candela to Lux Calculator Convert luminous intensity in candela to illuminance in lux at a given distance (inverse-square). Runs locally in your browser. Try it free.
- Foot-Candles to Lux Calculator Convert foot-candles (fc) to lux (lx): lx = fc × 10.76391. Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Lumen to Candela Calculator Convert lumens (lm) to candela (cd) using beam angle: cd = lm ÷ 2π(1 − cos(θ/2)). Reverse candela to lumens. Includes solid angle and full-sphere 4π.
- Lumen to Lux Calculator Convert lumens (lm) to lux (lx): lx = lm ÷ A. Use area in m² or ft², or isotropic sphere radius. Reverse lux to lumens. Runs locally in your browser.
- Lumen to Millicandela Calculator Convert lumens (lm) to millicandela (mcd): mcd = 1000 × lm ÷ 2π(1 − cos(θ/2)). Reverse mcd to lumens. Runs locally in your browser. Fast and free.
- Lumen to Watt Calculator Convert lumens (lm) to watts (W) using luminous efficacy: W = lm ÷ η (lm/W). Reverse watts to lumens. Includes typical LED, CFL, halogen, and incandescent.
- Lux to Candela Calculator Convert lux (lx) to candela (cd) at a distance: cd = lx × d² (meters) or cd = lx × d(ft)² ÷ 10.76391. Reverse candela to lux. Runs locally in your browser.
- Lux to Lumen Calculator Convert lux (lx) to lumens (lm): lm = lx × A. Use area in m² or ft², or isotropic sphere radius. Reverse lumens to lux. Runs locally in your browser.
- Lux to Watt Calculator Convert lux (lx) to watts (W): W = (lx × A) ÷ η. Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Watt to Lumen Calculator Convert watts (W) to lumens (lm): lm = W × η (lm/W). Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.
- Watt to Lux Calculator Convert watts (W) to lux (lx): lx = (W × η) ÷ A. Free online tool — no sign-up. Clear formulas and worked examples. Runs locally in your browser.