Electrical calculator

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.

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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 · 3/3 declared partitions (mah-wh, wh-mah, invalid-domain) · Matrix
Known limitations: Nominal cell voltage; no Peukert / temperature
Core CVP does not include live graph, viewport, or pointer interaction.
Model: Battery energy in Wh from mAh and volts, or capacity in mAh from Wh and volts.
Scope: Voltage is the nominal basis for the mAh rating
Verification: Engine tested · Source checked · v1.3.1 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Versions: Calculation 1.3.1 · CVP protocol 1.0.0-proposed
CVP identity: 3/3 property · digest 2c76023a51c7
Legacy regression: 13/13 tests · Production surface contract 4/4
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: Internal · Pass · electrical-engineer
Named expert review: Not performed
CVP suite: 2/2 golden · 2/2 CVP boundary · 2/2 invalid · 3/3 property · 1/1 cross-interface · 1/1 CVP contract · Manifest
Sources: IEC 60050 — International Electrotechnical Vocabulary — Electric charge (IEV 113-02-10)
IEC 60050 — International Electrotechnical Vocabulary — Watt hour (IEV 131-11-58)
BIPM SI Brochure (9th edition, version 4.01) — Coulomb, watt-hour, and volt
NIST Guide to the SI (SP 811) — Joule, watt-hour, and ampere-hour relationships
Battery industry convention — Nominal voltage basis for mAh ratings
Sources
Evidence: 8 legacy golden · 2 legacy boundary · legacy regression suite · 2/2 oracle-backed golden · 2/2 invalid · Artifact integrity PASS · CalculatorX electrical review
Semantic contract: PASS

Full verification

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

Formulas

Core equations used by this calculator.

mAh → WhWh = mAh × V ÷ 1000

Wh → mAhmAh = Wh × 1000 ÷ V

Via AhAh = mAh ÷ 1000 ··· Wh = Ah × V

i1 Ah = 1000 mAh. Energy and charge are different quantities — voltage is required. Nameplate mAh on power banks is often at the internal cell voltage (~3.6–3.7 V); USB 5 V output energy is lower after conversion losses.

How to use

Choose mAh → Wh or Wh → mAh

Forward needs charge and voltage; reverse needs energy and voltage.

Enter capacity (or Wh) and voltage

Use nominal battery voltage from the datasheet or label.

Read Wh or mAh

Wh is better for comparing energy across different voltages; mAh alone is not.

Example calculations

Common configurations with formula and result.

Smartphone battery

5,000 mAh · 3.7 V

5000 × 3.7 ÷ 1000

18.5 Wh

Small power bank

10,000 mAh · 3.7 V

10000 × 3.7 ÷ 1000

37 Wh

Large power bank

26,800 mAh · 3.7 V

26800 × 3.7 ÷ 1000

99.16 Wh

USB pack at 5 V

300 mAh · 5 V

300 × 5 ÷ 1000

1.5 Wh

C cell

8,000 mAh · 1.5 V

8000 × 1.5 ÷ 1000

12 Wh

Wh → mAh

1.5 Wh · 5 V

1.5 × 1000 ÷ 5

300 mAh

Common batteries (illustrative)

Common values at a glance.

Battery	Typical mAh	Voltage	Energy (Wh)
AAA	1,200	1.5 V	1.8 Wh
AA	2,700	1.5 V	4.05 Wh
C	8,000	1.5 V	12 Wh
D	12,000	1.5 V	18 Wh
9V	565	9 V	5.085 Wh
Phone (Li-ion)	5,000	3.7 V	18.5 Wh
Power bank	10,000	3.7 V	37 Wh
Power bank	26,800	3.7 V	99.2 Wh

i Capacities vary by chemistry and brand. Wh = mAh × V ÷ 1000. Power-bank mAh is usually at cell voltage, not USB 5 V.

mAh to Wh calculator specification

Version 1.3.1 · Engine tested · Supplemental domain review · Internal · 2026-08-08

Calculation status

Engine tested 13/13 tests · Production surface contract 4/4
Supplemental domain review Internal · Pass · electrical-engineer · 2026-08-08
Named expert review Not performed
Calculation version 1.3.1

Review policy · Evidence · Reviewed by CalculatorX electrical review (electrical-engineer)

Definition: Milliamp-hours (mAh) measure electric charge (how much current a battery can deliver over time). Watt-hours (Wh) measure energy. Converting between them requires voltage: Wh = mAh × V ÷ 1000. Use the cell’s nominal voltage (often 3.7 V for Li-ion), not necessarily the USB output voltage.
What it calculates: Battery energy in Wh from mAh and volts, or capacity in mAh from Wh and volts.
Inputs: Charge Q (mAh) or energy E (Wh)
Voltage V (V)
Outputs: Energy in watt-hours (Wh)
Capacity in milliamp-hours (mAh)
Formula: E=Q·V/1000; Q=E·1000/V
Assumptions: Voltage is the nominal basis for the mAh rating
Conversion ignores charge/discharge efficiency and Peukert effects
Units: mAh, V → Wh
Boundary conditions: Zero voltage on mAh→Wh (scale-product) yields 0 Wh — soft boundary
Zero voltage on Wh→mAh (scale-quotient) yields 0 mAh — soft boundary
Zero mAh yields 0 Wh
Ignores charge/discharge efficiency and Peukert effects
Example: 5000 mAh × 3.7 V ÷ 1000 = 18.5 Wh
Validation cases: 12 published on this page · 13/13 tests · Production surface contract 4/4 · View evidence
5000 mAh, 3.7 V → 18.5 Wh
10000 mAh, 3.7 V → 37 Wh
300 mAh, 5 V → 1.5 Wh
8000 mAh, 1.5 V → 12 Wh
1.5 Wh, 5 V → mAh → 300 mAh
10000 mAh, 3.7 V (2× of 5000) → 37 Wh (linear in mAh)
5000 mAh, 7.4 V (2× V) → 37 Wh (linear in V)
5000 mAh, 0 V → error VOLTAGE_MUST_BE_POSITIVE
1.5 Wh, 0 V → mAh → error VOLTAGE_MUST_BE_POSITIVE
0 mAh, 3.7 V → 0 Wh
0 Wh, 5 V → mAh → 0 mAh
5000 mAh → Wh → mAh round-trip at 3.7 V → 5000 mAh
Sources: IEC 60050 — International Electrotechnical Vocabulary — Electric charge (IEV 113-02-10) · accessed 2026-09-05
Supports: Electric charge Q; coherent SI unit coulomb. Note: 1 A·h = 3.6 kC is used for electrolytic devices / batteries
IEC 60050 — International Electrotechnical Vocabulary — Watt hour (IEV 131-11-58) · accessed 2026-09-05
Supports: 1 Wh ≔ 3600 J. At constant terminal voltage, E(Wh) = Q(Ah)×V from W = ∫v i dt
BIPM SI Brochure (9th edition, version 4.01) — Coulomb, watt-hour, and volt · 2026-06 · DOI · accessed 2026-09-05
Supports: Unit scaling mAh → Ah (10⁻³); Wh = A·h × V at constant V
NIST Guide to the SI (SP 811) — Joule, watt-hour, and ampere-hour relationships
Supports: Wh = mAh × V / 1000; Q = Wh × 1000 / V
Battery industry convention — Nominal voltage basis for mAh ratings
Supports: Conversion uses stated nominal V; ignores efficiency and Peukert effects
Last reviewed: 2026-08-08
Reviewed by: CalculatorX electrical review (electrical-engineer)
Calculation version: 1.3.1

Background

Interpretation and common distinctions.

Convert milliamp-hours (mAh) to watt-hours (Wh) — or reverse — using battery voltage:

E((Wh)) = (Q((mAh)) × V((V)))/1000 Q((mAh)) = (E((Wh)) × 1000)/(V((V)))

Default example: 5,000 mAh at 3.7 V → 18.5 Wh.

Why voltage is required

Unit	Measures	Role
mAh	Electric charge / capacity	How much current × time the cell can supply
Wh	Energy	Total energy available to a load
V	Voltage	Links charge to energy

mAh alone does not tell you energy. A high-mAh low-voltage pack can store less energy than a lower-mAh higher-voltage pack.

Power banks and USB voltage

Marketing mAh is usually rated at the internal Li-ion cell (~3.7 V). USB ports deliver ~5 V after a boost converter, so usable mAh at 5 V is lower, and real runtime is reduced further by efficiency losses. Comparing packs by Wh (when labeled) is more reliable than by mAh alone.

Supported and not supported

Supported — mAh↔Wh via nominal voltage · API electrical.mah_to_wh

Not supported — Peukert, charge efficiency, multi-chemistry auto V

Agent / API notes

Capability id: electrical.mah_to_wh · tool id: mah-to-wh · pin calculation_version: 1.3.1.

Stable errors: MISSING_REQUIRED_INPUT, INVALID_NUMBER, VALUE_MUST_BE_NON_NEGATIVE, VOLTAGE_MUST_BE_POSITIVE, INVALID_MODE.

Other calculators in this family: kWh to Watts, kWh to kW, Energy consumption, Energy cost, Watts to Joules .

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Frequently asked questions

Key distinctions behind the calculation.

How do I convert mAh to Wh?

Multiply milliamp-hours by voltage, then divide by 1000: Wh = (mAh × V) ÷ 1000. Example: 5,000 mAh × 3.7 V ÷ 1000 = 18.5 Wh.

Why do I need voltage?

mAh is charge; Wh is energy. Energy = charge × voltage (with unit scaling). Two batteries with the same mAh but different voltages store different energy.

How do I convert Wh to mAh?

mAh = (Wh × 1000) ÷ V. Example: 1.5 Wh at 5 V → 1.5 × 1000 ÷ 5 = 300 mAh.

What voltage should I use for a Li-ion phone battery?

Usually the nominal cell voltage, about 3.6–3.7 V (sometimes listed as 3.8 V). Do not use the charger’s 5 V USB rating unless the mAh figure is specified at 5 V.

Why is Wh better than mAh for comparing power banks?

mAh depends on voltage. Wh (or Wh on airline labels) compares stored energy fairly across packs. A higher mAh at lower voltage can have less energy than a smaller mAh at higher voltage.

Is 10,000 mAh at 3.7 V the same as at 5 V?

No. 10,000 mAh × 3.7 V ÷ 1000 = 37 Wh. At 5 V that same energy is only 37 × 1000 ÷ 5 = 7,400 mAh equivalent — and real USB output is lower due to conversion losses.

How do mAh and Ah relate?

1 Ah = 1000 mAh. Wh = Ah × V is equivalent to Wh = mAh × V ÷ 1000.