HomeCalculatorsElectricalPower & EnergyAmps to Volts Calculator
Electrical calculator

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.

Instant result
Result
—

Enter values to calculate.

Inputs—
Mode—
Formula—
Trust summary CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance
Input interpretation
Enter values to calculate.
Result
—
Assurance
Engineering
Declared partition coverage
PASS · 8/8 declared partitions (a-v-ohm, v-a-ohm, a-v-watt-dc, a-v-watt-ac_single, a-v-watt-ac_three, v-a-watt, invalid-domain, round-trip) · Matrix
Known limitations
  • Engineering applicability: DC / AC 1φ / AC 3φ L-L
  • Core CVP does not include live graph, viewport, or pointer interaction.
Model
Voltage from current plus watts or ohms; current from voltage plus watts or ohms; watts paths select DC / AC 1φ / AC 3φ L-L with PF on AC.
Scope
Ohms path assumes resistive Ohm’s-law behavior.
Verification
Engine tested · Source checked · v1.4.2 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Versions
Calculation 1.4.2 · CVP protocol 1.0.0-proposed
CVP identity
11/11 property · digest b787583c1faa
Legacy regression
42/42 tests · Production surface contract 36/36
Reference
O1 model · O2 expected_values · O2 numerical_behavior
Interfaces
PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session.
Supplemental domain review
Not performed
Named expert review
Not performed
CVP suite
7/7 golden · 20/20 CVP boundary · 18/18 invalid · 11/11 property · 2/2 round-trip · 2/2 cross-interface · 36/36 CVP contract · Manifest
Sources
Sources
Evidence
11 legacy golden · 20 legacy boundary · legacy regression suite · 7/7 oracle-backed golden · 18/18 invalid · Artifact integrity PASS
This calculator CURRENT · Public schema 1.4.2 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓
Semantic contract
PASS
Full verification

Manifest identity, reference classes, interfaces, suite, and production records.

Formulas

Core equations used by this calculator.

With watts (DC)V = P ÷ I
With ohmsV = I × R
AC 1φ (watts)V = P ÷ (I × PF)
AC 3φ (watts)V = P ÷ (√3 × I × PF)
iAmps alone are not enough. Use the ohms tab when you know resistance; use the watts tab when you know power. Watts paths select DC, AC single-phase, or balanced AC three-phase (line-to-line). Canonical Agent schema forbids power_factor on DC; REST may still send it and it is ignored with a warning. Ohms path is resistive Ohm’s-law behavior.

How to use

1

Choose ohms or watts

A → V (ohms) needs resistance; A → V (watts) needs power. Reverse tabs find current.

2

Enter the known values

On watts tabs, choose DC, AC 1φ, or AC 3φ. DC hides power factor. AC uses RMS voltage/current.

3

Read the voltage (or current)

The result updates as you type.

Example calculations

Common configurations with formula and result.

ϟ

From power

120 W · 10 A

V = 120 ÷ 10
12 V
ϟ

From resistance

1.2 A · 20 Ω

V = 1.2 × 20
24 V
ϟ

USB-style load

65 W · 13 A

V = 65 ÷ 13
5 V
ϟ

AC 1φ with PF

600 W · 6.25 A · PF 0.8

V = 600 ÷ (6.25 × 0.8)
120 V
ϟ

AC 3φ

10 kW · 15.5 A · PF 0.9

V = 10000 ÷ (√3 × 15.5 × 0.9)
≈ 413.9 V

Examples (V = P ÷ I, PF = 1)

Common values at a glance.

Power (W)Current (A)Voltage (V)
60320
1201012
120524
2401024
65135
15006.5231
20008.33240
10005200
i Ohm’s-law examples: 1.2 A × 20 Ω = 24 V; 2 A × 12 Ω = 24 V.

Amps to Volts calculator specification

Version 1.4.2 · Engine tested

Calculation status

Review policy · Evidence

Definition
You cannot convert amps to volts from current alone — you also need power in watts or resistance in ohms. This calculator finds voltage from V = I × R (Ohm’s law) or V = P ÷ I (watts path, with DC / AC 1φ / AC 3φ L-L), and can reverse the conversion to find current.
What it calculates
Voltage from current plus watts or ohms; current from voltage plus watts or ohms; watts paths select DC / AC 1φ / AC 3φ L-L with PF on AC.
Inputs
  • Current I (A) and resistance R (Ω), or
  • Power P (W) and current I (A) [+ system and PF for AC], or reverse pairs for amps
Outputs
  • Voltage in volts
  • Current in amperes (reverse modes)
Formula
V=I·R or V=P/I; AC 1φ: V=P/(I·PF); AC 3φ L-L: V=P/(√3·I·PF)
Assumptions
  • Ohms path assumes resistive Ohm’s-law behavior.
  • Watts DC matches P = V·I. Watts AC uses RMS and total power factor λ.
  • Three-phase watts path assumes balanced line-to-line voltage.
  • DC does not use power factor or phase. Canonical Agent schema forbids power_factor on DC; REST may send it and it is ignored with POWER_FACTOR_IGNORED.
  • JSON Schema is a callable-input envelope (types, required fields, enums). Zeros and out-of-range PF may be schema-valid; the engine returns stable error codes.
Units
  • A, W, Ω → V
Boundary conditions
  • Watts A→V: P>0 and I=0 → CURRENT_MUST_BE_NONZERO (not 0 V)
  • Watts A→V: P=0 and I=0 → UNDEFINED (0/0 indeterminate)
  • Ohms reverse: V≠0 and R=0 → RESISTANCE_MUST_BE_NONZERO (not 0 A)
  • Ohms reverse: V=0 and R=0 → UNDEFINED
  • Ohms forward (product): I=0 or R=0 → 0 V (valid multiplication)
  • Zero power with I>0 → 0 V
  • AC power_factor is required and must be in (0, 1]. UI initializes AC PF to 1.0; Agent/API clients must send it. Omitted AC PF → MISSING_REQUIRED_INPUT. Explicit PF≤0 or PF>1 → POWER_FACTOR_OUT_OF_RANGE
  • IEEE-754 binary64; non-finite overflow → NON_FINITE_RESULT
  • Canonical Agent fields are mode, current, resistance, power, voltage, system, power_factor; DC must omit power_factor; REST still accepts a, b, phase, pf (DC PF ignored with POWER_FACTOR_IGNORED)
Numerical precision
  • IEEE-754 binary64 (IUT and O2 reference oracle)
  • CVP-NUM-01 tolerance: ≤2 ULP vs independent O2 oracle; declared_before_evaluation=true
  • Non-finite results → NON_FINITE_RESULT (not Infinity/NaN success)
Example
120 W ÷ 10 A = 12 V; 2 A × 12 Ω = 24 V
Validation cases

19 published on this page · 42/42 tests · Production surface contract 36/36 · View evidence

  • 120 W, 10 A, DC → 12 V
  • 1.2 A, 20 Ω → 24 V
  • 65 W, 13 A → 5 V
  • 600 W, 6.25 A, PF 0.8, AC 1φ → 120 V
  • 10000 W, 15.5 A, PF 0.9, AC 3φ → ≈413.9 V
  • 24 V, 12 Ω → A → 2 A
  • 120 W, 12 V, DC → A → 10 A
  • 240 W, 10 A, DC (2× P) → 24 V (linear in P)
  • 120 W, 5 A, DC (half I) → 24 V (inverse in I)
  • 120 W, 0 A, DC → error CURRENT_MUST_BE_NONZERO
  • 0 W, 0 A, DC → error UNDEFINED
  • 0 W, 10 A, DC → 0 V
  • 600 W, 6.25 A, PF 0, AC 1φ → error POWER_FACTOR_OUT_OF_RANGE
  • 600 W, 6.25 A, AC 1φ, omitted PF → error MISSING_REQUIRED_INPUT
  • 2 A, 0 Ω → 0 V
  • 24 V, 0 Ω → A → error RESISTANCE_MUST_BE_NONZERO
  • 0 V, 0 Ω → A → error UNDEFINED
  • 120 W → 12 V → A round-trip at DC → 10 A
  • 120 W, 10 A, DC, PF 0.5 (Agent schema invalid; REST ignores PF) → 12 V (REST) / schema reject (Agent)
Sources
  • Watt’s law / power identity — Real power P = V × I × PF (1φ); P = √3 × V × I × PF (3φ L-L)
    Supports: V = P/(I·PF); I = P/(V·PF); 3φ with √3
  • Ohm’s law — Ohmic conductors V = I × R
    Supports: A→V (ohms) and V→A (ohms) modes
  • IEC 60050 — International Electrotechnical Vocabulary — Active power (IEV 131-11-42) · accessed 2026-09-05
    Supports: P is active power; unit watt (W). Watts-path voltage uses P, not apparent power S.
  • IEC 60050 — International Electrotechnical Vocabulary — Power factor (IEV 131-11-46) · accessed 2026-09-05
    Supports: λ = |P| / S; AC watts path V = P / (I·λ) (1φ) or V = P / (√3·I·λ) (3φ L-L)
  • IEEE Std 1459-2025 — Power factor in AC real-power calculations · 2025-05-16 · errata checked · accessed 2026-09-05
    Supports: PF scaling on watts paths; PF = 1 for DC/resistive
  • BIPM SI Brochure (9th edition, version 4.01) — SI units for ampere, volt, ohm, and watt · 2026-06 · DOI · accessed 2026-09-05
    Supports: SI definitions and dimensional relationships among V, A, Ω, and W
  • NIST Guide to the SI (SP 811) — Volt, ampere, ohm, watt
    Supports: SI unit relationships for V, A, Ω, W
  • CalculatorX amps-volts-reference oracle (O2) — Separate-module Node arithmetic — same V8 binary64 runtime as IUT (not language-isolated); scripts/lib/cvp/oracles/amps-volts-reference.mjs
    Supports: expected_values + numerical_behavior (≤2 ULP); not transcribed from IUT
Calculation version
1.4.2

Background

Interpretation and common distinctions.

You need watts or ohms

Amps alone do not determine volts. Voltage depends on how much power the load uses or how much resistance is in the path:

Method Formula When to use
Power V = P ÷ I You know watts and amps (DC / resistive)
Resistance V = I × R You know current and ohms (Ohm’s law)
AC 1φ V = P ÷ (I × PF) Single-phase real power
AC 3φ V = P ÷ (√3 × I × PF) Three-phase, line-to-line

Quick reference (PF = 1)

Power (W) Current (A) Voltage (V)
60 3 20
120 5 24
120 10 12
240 10 24
65 13 5
500 25 20
1000 5 200
1500 6.5 ≈231
2000 8.33 240

Notes for AC vs DC

  • DC: V = P/I or V = IR. Canonical Agent schema forbids power_factor. REST may still send it; the engine ignores it and emits POWER_FACTOR_IGNORED.
  • AC 1φ / AC 3φ: power_factor is required and must be in (0, 1]; three-phase uses √3 and line-to-line RMS voltage. The UI initializes AC PF to 1.0; Agent/API clients must send it.
  • Nameplate watts are real power; for apparent-power sizing see Amps to VA.

Supported and not supported

Supported — Amps↔volts via Ohm’s law or real power for DC, AC single-phase, and balanced three-phase L-L · API electrical.amps_to_volts (engine amps-volts)

Not supported — Unbalanced three-phase; converting amps to volts from current alone; reactive impedance networks on the ohms path

Agent / API notes

Capability id: electrical.amps_to_volts · tool id: amps-to-volts · pin 1.4.2.

Canonical Agent inputs use mode (a-v-ohm | a-v-watt | v-a-ohm | v-a-watt), then current / resistance / power / voltage as required by the mode, plus system (dc | ac_single | ac_three). AC watts paths require power_factor; DC watts payloads must omit it. REST still accepts a/b, phase, and pf; a DC PF is ignored with POWER_FACTOR_IGNORED. Output unit is V for A→V modes and A for V→A modes. Pin the immutable schema at /schemas/electrical.amps_to_volts/1.4.2/input.json; /schemas/electrical.amps_to_volts.input.json is the latest alias. JSON Schema is a callable-input envelope: current = 0 is schema-valid and the engine returns CURRENT_MUST_BE_NONZERO.

Stable errors: MISSING_REQUIRED_INPUT, INVALID_NUMBER, INVALID_MODE, INVALID_PHASE, CURRENT_MUST_BE_NONZERO, RESISTANCE_MUST_BE_NONZERO, VOLTAGE_MUST_BE_POSITIVE, POWER_FACTOR_OUT_OF_RANGE, UNDEFINED, VALUE_MUST_BE_NON_NEGATIVE, NON_FINITE_RESULT.

CVP (Calculator Verification Protocol)

Engineering pilot under CVP 1.0 Proposed. Profile: engineering.

  • Evidence Manifest: /evidence/electrical.amps_to_volts/1.4.2.cvp.json (schema: /developers/cvp/schema)
  • Independent reference: O1 (model) + O2 separate module for expected_values and numerical_behavior — golden expectations are not copied from the IUT; O2 shares Node/V8 binary64 with the IUT (common-mode risk acknowledged; O3 optional)
  • Numerical policy: IEEE-754 binary64; ≤2 ULP vs O2; declared_before_evaluation=true
  • Coverage partitions: a-v-ohm, v-a-ohm, a-v-watt×{dc,ac_single,ac_three}, v-a-watt, invalid-domain, round-trip
  • Trust Summary collapsed peek is CVP-first (CVP VERIFIED · Proposed 1.0 · engineering · …); expanded Verification includes the same badge — never a bare CVP VERIFIED while Proposed; VERIFIED also requires production attestation CURRENT

CVP does not imply third-party certification or fitness for every real-world installation.

Other calculators in this family: Amps to kW Calculator, Amps to VA Calculator, Electric Power Calculator, Energy Consumption Calculator, Energy Cost Calculator, eV to Volts Calculator, kVA to Amps Calculator, kVA to kW Calculator . Explore all Power & Energy.

→ 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. › → 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. › → 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. › → 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. ›
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Frequently asked questions

Key distinctions behind the calculation.

How do I convert amps to volts?

You need a second quantity. With power: V = P ÷ I. With resistance: V = I × R. Amps alone are not enough.

Can I convert amps to volts without watts?

Yes, if you know resistance: V = I × R (Ohm’s law). Without watts or ohms, voltage cannot be determined from current alone.

What is the difference between the two methods?

Watts path uses the power formula V = P/I (extend with PF and √3 for AC). Ohms path uses Ohm’s law V = IR, typical for DC resistive circuits.

How does power factor change the result?

For AC real power, V = P ÷ (I × PF) single-phase, or V = P ÷ (√3 × I × PF) three-phase. DC does not use PF. Canonical Agent schema forbids power_factor on DC; REST may still send it (ignored with POWER_FACTOR_IGNORED). On AC, power_factor is required and must be in (0, 1]. The UI initializes AC PF to 1.0; Agent/API clients must send it. Explicit PF = 0, PF < 0, or PF > 1 returns POWER_FACTOR_OUT_OF_RANGE rather than silently becoming 1.

What happens if current or resistance is zero?

V = I × R may be 0 V when I = 0 or R = 0. Division is different: P > 0 with I = 0, or V ≠ 0 with R = 0, is undefined and returns an error. 0 ÷ 0 is indeterminate.

What are amps and volts?

Amps measure current (charge flow). Volts measure electric potential — the “pressure” that pushes current through a resistance.

Why is this conversion useful?

It helps check supply voltage from a known load, size batteries and solar strings, and verify Ohm’s-law relationships in circuits.

How do I get amps from volts?

Use V → A (ohms): I = V ÷ R, or V → A (watts): I = P ÷ (√3 (3φ only) × V × PF).