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mAh to Wh Calculator
Convert battery capacity from mAh to watt-hours and amp-hours, check the 100 Wh airline carry-on limit and estimate how many phone charges a power bank gives.
How to use it
- Enter the capacity printed on the battery or power bank in mAh and its nominal voltage (3.6-3.7 V for lithium-ion cells).
- Enter your phone battery size to see how many full charges to expect.
- Use 70-80 percent efficiency, because voltage conversion and heat lose part of the energy.
How it works
Watt-hours = mAh ÷ 1,000 × nominal voltage. A 20,000 mAh power bank at 3.7 V holds 74 Wh. Amp-hours are mAh ÷ 1,000. Power banks are labelled with the cell capacity at 3.6-3.7 V, not at the 5 V output, which is why a 10,000 mAh bank cannot deliver 10,000 mAh at 5 V.
Most airlines allow lithium batteries up to 100 Wh in carry-on baggage without approval and 100-160 Wh with airline approval; spare batteries must go in hand luggage, never in checked bags. Check your airline and the label on the device.
FAQ
Is a 20,000 mAh power bank allowed on a plane?
Yes, at 3.7 V it is 74 Wh, below the 100 Wh limit. Banks above about 27,000 mAh at 3.7 V exceed 100 Wh and need airline approval.
How many times can a 10,000 mAh power bank charge a phone?
With a 4,500 mAh phone battery and about 75 percent efficiency, roughly 1.6 full charges.
How do I convert mAh to Wh?
Divide mAh by 1,000 and multiply by the voltage: 5,000 mAh × 3.7 V ÷ 1,000 = 18.5 Wh.
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