There is no single mAh equivalent of 100 Wh. Divide 100,000 by the nominal battery voltage: at 3.7 V, 100 Wh is approximately 27,027 mAh; at 3.85 V it is approximately 25,974 mAh.
The reverse calculation
mAh = Wh × 1,000 ÷ V. For a 100 Wh threshold at 3.7 V, calculate 100 × 1,000 ÷ 3.7. This is a mathematical conversion, not a guarantee that a device is accepted on every flight.
Why 26,800 mAh is a useful example
26,800 × 3.7 ÷ 1,000 = 99.16 Wh. The same mAh at 3.85 V would be 103.18 Wh. Always use the nominal voltage associated with the stated battery capacity, not a USB output setting.
Do not round a device into the allowance
At 3.7 V, a 27,100 mAh battery stores 100.27 Wh. Rounding that number to 100 does not make it a 100 Wh battery. Use the exact calculation and the manufacturer’s marked Wh rating.
100 Wh to mAh: how big is a flight-friendly power bank?
There is no single mAh equivalent of 100 Wh. Divide 100,000 by the nominal battery voltage: at 3.7 V, 100 Wh is approximately 27,027 mAh; at 3.85 V it is approximately 25,974 mAh.
The reverse calculation
mAh = Wh × 1,000 ÷ V. For a 100 Wh threshold at 3.7 V, calculate 100 × 1,000 ÷ 3.7. This is a mathematical conversion, not a guarantee that a device is accepted on every flight.
Why 26,800 mAh is a useful example
26,800 × 3.7 ÷ 1,000 = 99.16 Wh. The same mAh at 3.85 V would be 103.18 Wh. Always use the nominal voltage associated with the stated battery capacity, not a USB output setting.
Do not round a device into the allowance
At 3.7 V, a 27,100 mAh battery stores 100.27 Wh. Rounding that number to 100 does not make it a 100 Wh battery. Use the exact calculation and the manufacturer’s marked Wh rating.
Where can I check the official rule?
Use the FAA PackSafe — battery ratings source linked above and confirm with every operating airline on your itinerary.
Independent guidance, not airline approval. Confirm with your operating airline before travel. Report a correction.
