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mAh to Wh converter

Convert the capacity of a battery or power bank from milliamp-hours (mAh) to watt-hours (Wh), or the other way round. You also see whether it is allowed on a plane.

Convert

In mAh or in Wh, depending on your choice.

Empty = 3.7 V, the cell voltage of lithium-ion batteries.

Fill in the fields; the answer appears here straight away.

How it works

  1. Enter the values

    Type the numbers or the formula. Decimals may use a point or a comma. No idea? Click Fill in an example.

  2. Instant answer

    The answer appears as you type, with the most important intermediate values.

  3. See the working

    Under "How it's worked out" you see the steps, handy for checking your own calculation.

How to convert mAh to Wh

Wh = mAh × V ÷ 1000. A 20,000 mAh power bank at 3.7 V holds 20,000 × 3.7 ÷ 1000 = 74 Wh. The other way round: mAh = Wh × 1000 ÷ V.

mAh only measures charge; you need the voltage to know how much energy is stored. That is why batteries with different voltages can only be compared in Wh.

Which voltage?

Lithium-ion cells have a nominal voltage of 3.6 to 3.7 V (3.85 V in many modern phones). Power banks quote their mAh at that cell voltage, not at the 5 V of the USB output. If you leave the voltage empty, we use 3.7 V.

Can I take the battery on a plane?

For lithium batteries in hand luggage, the limits (ICAO/IATA) are:

  • up to 100 Wh: allowed;
  • 100 to 160 Wh: only with the airline's approval;
  • above 160 Wh: not allowed.

A 27,000 mAh power bank (99.9 Wh) just stays under the limit; a 30,000 mAh one (111 Wh) needs approval. Power banks always go in your hand luggage, never in the hold. Rules can differ per airline, so check before you fly.

Frequently asked questions

Is the mAh to Wh free?

Yes. The mAh to Wh is completely free, with no account, sign-up or usage limit.

How accurate is the result?

The tool calculates with your browser's number precision. For important calculations, always double-check what you entered.

Does it work on my phone?

Yes. The tool works in any modern browser on a phone, tablet or computer.