Power bank watt-hour calculator

The label shows mAh; airlines set limits in Wh. Wh = mAh × V ÷ 1,000.

Capacity (mAh)

Voltage (V)

…or Wh from the label

How many power banks

Airline

Quick reference

Label	At 3.7 V	Verdict
5,000 mAh	18.5 Wh	Allowed in the cabin
10,000 mAh	37 Wh	Allowed in the cabin
20,000 mAh	74 Wh	Allowed in the cabin
26,800 mAh	99.2 Wh	Allowed in the cabin
30,000 mAh	111 Wh	Needs airline approval (many refuse)
40,000 mAh	148 Wh	Needs airline approval (many refuse)
50,000 mAh	185 Wh	Not allowed

Rules: FAA, UK CAA, EASA, CASA and IATA 2026 guidance, plus each airline's own page. See power banks on every airline.