mAh to Wh Calculator

Convert milliamp-hours (mAh) to watt-hours (Wh), or reverse Wh to mAh, using the battery's nominal voltage. The calculator shows the substituted formula, common battery conversions and a lithium-battery air-travel reference.

Maintained byGiorgi Gaprindashvili PublishedJune 27, 2026 UpdatedAugust 6, 2026 Technical reviewAugust 2026

Common capacities

Common nominal voltages

Capacity (mAh)

Enter the capacity exactly as printed on the battery or power bank.

Nominal voltage (V)

Use the voltage tied to the capacity rating, not automatically the output voltage.

Method based on Wh = Ah x V; mAh is Ah / 1000 · reviewed August 2026 · revision 1.1

Common mAh to Wh conversions at 3.7 V

The table uses the selected nominal voltage. At 3.7 V it covers the power-bank capacities appearing most often in searches, without pretending that voltage is optional.

Capacity	Nominal voltage	Energy	Air-travel reference
1,000 mAh	3.7 V	3.7 Wh	0-100 Wh
5,000 mAh	3.7 V	18.5 Wh	0-100 Wh
10,000 mAh	3.7 V	37 Wh	0-100 Wh
20,000 mAh	3.7 V	74 Wh	0-100 Wh
25,000 mAh	3.7 V	92.5 Wh	0-100 Wh
30,000 mAh	3.7 V	111 Wh	101-160 Wh

The travel column is a threshold reference for rechargeable lithium batteries, not an approval. Check the airline and the current rules before travel.

Same mAh can mean different energy

Both examples have the same 5000 mAh charge rating. The 3.7 V cell stores 18.5 Wh while the 3.2 V cell stores 16 Wh, so voltage is required for a meaningful energy comparison.

How the conversion works

A milliamp-hour is a unit of charge. A watt-hour is a unit of energy. Multiplying charge by voltage turns the battery's charge rating into stored energy:

mAh to WhWh = mAh × V ÷ 1000

Wh to mAhmAh = Wh × 1000 ÷ V

For example, 5000 mAh at 3.7 V is 18.5 Wh. The same 5000 mAh at 3.2 V is 16 Wh. That is why batteries with identical mAh ratings can store different amounts of energy.

Use the voltage tied to the capacity rating

The conversion is only as accurate as the voltage entered. Use the battery's nominal voltage, normally printed on the label or data sheet. Do not use the fully charged peak voltage unless the capacity was explicitly specified at that voltage.

Chemistry or pack	Typical nominal voltage	Important distinction
Li-ion / LiPo cell	3.6-3.7 V	Often 4.2 V when fully charged; use the rating on the label.
LiFePO4 cell	3.2 V	A four-cell series pack is commonly rated 12.8 V.
NiMH / NiCd cell	1.2 V	Multiply by the number of cells in series for pack voltage.
Alkaline cell	1.5 V	Voltage falls during discharge and under load.
Lead-acid cell	2.0 V	A six-cell battery is normally called a 12 V battery.

The power-bank voltage trap

Power banks usually advertise mAh at the internal lithium-cell voltage, commonly 3.7 V, while the USB port outputs 5 V or more. A 10000 mAh rating at 3.7 V is 37 Wh. Multiplying the same mAh by the 5 V USB output would claim 50 Wh and overstate the stored energy. Use the voltage that belongs to the printed mAh rating.

Can mAh be converted to watts?

Not directly. mAh measures charge, while watts measure power at an instant. Voltage lets you convert mAh to watt-hours. To estimate average watts, you must also know a time interval:

Average W = Wh ÷ hours

A 74 Wh battery delivering its energy evenly over 10 hours averages 7.4 W. Real loads vary, and conversion losses reduce the useful energy available to the device.

Lithium-battery air-travel thresholds

Current FAA guidance uses watt-hour bands for rechargeable batteries on passenger aircraft:

0-100 WhGenerally permitted under the FAA 100 Wh limit. Spare lithium batteries and power banks must be carry-on only.

101-160 WhAir-carrier approval is required. FAA guidance limits passengers to two spare batteries in this band.

Over 160 WhNot permitted as ordinary passenger baggage under the general rule, apart from separate mobility-device provisions.

Airlines and countries may be stricter. Confirm the label, battery condition, quantity and current carrier rules before travel.

Nominal energy is not usable energy

The result is the battery's nominal stored energy. Usable output is lower because voltage conversion produces heat, internal resistance wastes energy under load, cold temperatures reduce deliverable capacity, cells age, and devices stop at a cut-off voltage. Use the Wh result to compare labels and perform first-pass sizing, not as a guarantee of runtime.

Where this conversion is useful

Compare batteries fairly

Watt-hours include voltage, so they let you compare the stored energy of cells and packs that have different voltages.

Check lithium-battery travel limits

Passenger-baggage rules use watt-hours. The calculator flags the common 100 Wh and 160 Wh thresholds, but the airline's current rules still control.

Read power-bank and device labels

Power banks often advertise mAh at the internal cell voltage. Converting that rating to Wh avoids confusing the 3.7 V cell with the 5 V USB output.

Frequently asked questions

How do I convert mAh to Wh?

Multiply milliamp-hours by the nominal voltage and divide by 1000: Wh = mAh x V / 1000. A 5000 mAh battery at 3.7 V is 18.5 Wh.

How do I convert mAh to kWh?

First convert mAh to Wh, then divide by 1000. The combined formula is kWh = mAh x V / 1,000,000. For example, 20000 mAh at 3.7 V is 0.074 kWh.

How many Wh is a 10000 mAh power bank?

At the common 3.7 V internal-cell rating, 10000 mAh is 37 Wh. Use the voltage tied to the printed capacity, not the 5 V USB output voltage.

How many Wh is a 20000 mAh power bank?

At 3.7 V, 20000 mAh is 74 Wh. Different nominal voltages produce different watt-hour values, so check the label.

Can I convert mAh directly to watts?

No. mAh measures charge and watts measure power. With voltage you can convert mAh to Wh. To estimate average watts you also need a time: W = Wh / hours.

Which voltage should I use for a power bank?

Use the voltage at which the mAh capacity is specified. For most lithium-ion power banks that is the internal cell's nominal 3.7 V, not the 5 V USB output.

Is a power bank under 100 Wh allowed on a plane?

Under current FAA guidance, rechargeable batteries up to 100 Wh are generally permitted on passenger aircraft; spare lithium batteries and power banks must be in carry-on baggage. Airlines can impose stricter rules, so verify before travel.

Will I actually get the calculated watt-hours?

The formula gives nominal stored energy. Usable energy is lower after conversion losses, internal resistance, temperature effects, battery aging and device cut-off voltage.

How this relates to other tools

Standard / tool	Relationship	What it means
All electrical converters	parent collection	Find the site's other unit and component-marking converters.
AWG to mm converter	battery-pack wiring reference	Battery current and conductor sizing are separate calculations; the wire converter helps translate gauge, diameter and area.

Related tools and standards

All electrical converters AWG to mm converter

Sources: FAA PackSafe - airline passengers and batteries · IATA - batteries and lithium-battery transport guidance. Verify against the current edition.