Watts (W) measure power; watt-hours (Wh) measure stored energy. A power bank advertised as 65 W or 100 W cannot be checked for flight capacity from that output number alone.
One label, different measurements
A label can show 20,000 mAh battery capacity, 3.7 V nominal voltage and 100 W maximum output. The capacity calculation is 20,000 × 3.7 ÷ 1,000 = 74 Wh. The 100 W output describes how fast energy can be supplied, not how much is stored.
Find the battery rating
Look for a printed Wh rating first. If you need to calculate it, pair the mAh capacity with its corresponding nominal voltage. Do not combine the internal battery’s mAh with a 5 V, 9 V or 20 V USB output specification.
Laptop power banks need the same check
Fast charging, USB-C PD and laptop compatibility describe features. They do not establish the stored-energy rating. Two products with the same charging wattage can have very different Wh capacities.
Power bank watts vs watt-hours: 100 W is not 100 Wh
Watts (W) measure power; watt-hours (Wh) measure stored energy. A power bank advertised as 65 W or 100 W cannot be checked for flight capacity from that output number alone.
One label, different measurements
A label can show 20,000 mAh battery capacity, 3.7 V nominal voltage and 100 W maximum output. The capacity calculation is 20,000 × 3.7 ÷ 1,000 = 74 Wh. The 100 W output describes how fast energy can be supplied, not how much is stored.
Find the battery rating
Look for a printed Wh rating first. If you need to calculate it, pair the mAh capacity with its corresponding nominal voltage. Do not combine the internal battery’s mAh with a 5 V, 9 V or 20 V USB output specification.
Laptop power banks need the same check
Fast charging, USB-C PD and laptop compatibility describe features. They do not establish the stored-energy rating. Two products with the same charging wattage can have very different Wh capacities.
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.
