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mAh to Wh Converter

Convert battery capacity between mAh and watt-hours (Wh = mAh × V ÷ 1,000) and check the airline power bank limits: up to 100 Wh in carry-on, 100–160 Wh with approval.

Convert

Capacity

Energy

Nominal voltage

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How it works

Wh = mAh × V ÷ 1,000 · mAh = Wh ÷ V × 1,000 · Ah = mAh ÷ 1,000 · 1 Wh = 3.6 kJ

Milliamp-hours measure charge, not energy: two batteries with the same mAh store different energy if their voltages differ. Multiplying by the nominal voltage gives watt-hours, the figure airlines, laptop makers and the UN transport rules use. FAA and IATA rules let passengers carry spare lithium-ion batteries and power banks only in carry-on baggage; up to 100 Wh is allowed freely, 100–160 Wh needs airline approval (normally two spares at most), and above 160 Wh is forbidden on passenger aircraft.

Worked example

A 20,000 mAh power bank with 3.7 V cells: 20,000 × 3.7 ÷ 1,000 = 74.0 Wh (20.00 Ah, 266.4 kJ). That is under 100 Wh, so it can go in your carry-on without airline approval, but never in checked baggage.

Sources: FAA PackSafe — Lithium batteries · IATA — Lithium battery guidance for passengers

Frequently asked questions

How do I convert mAh to Wh?

Multiply mAh by the voltage and divide by 1,000. A 10,000 mAh power bank at 3.7 V holds 37 Wh.

What is the largest power bank allowed on a plane?

Up to 100 Wh without approval — about 27,000 mAh at 3.7 V. Between 100 and 160 Wh (about 27,000–43,000 mAh) you need the airline’s approval. Always carry it in the cabin.