mAh to Wh Calculator & Flight Check
Convert a battery or power bank from mAh to Wh, then compare the result with the FAA passenger-flight battery bands. Always check your airline because it may apply stricter rules.
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Power banks and spare lithium batteries belong in carry-on baggage. Your airline may be stricter.
Compare a labeled power bank or measure delivered energy
The product’s printed Wh rating and the airline’s current policy—not this calculator—control whether it can travel.
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How it works
Watt-hours = mAh × volts ÷ 1,000. For example, a 20,000 mAh power bank at 3.7 V holds 74 Wh. The flight check then compares that energy with the FAA bands: up to 100 Wh; over 100 through 160 Wh; or over 160 Wh. It is a general check, not airline approval.
Common power bank sizes in watt-hours
These examples use a 3.7 V nominal lithium-cell rating. Use the voltage and Wh printed on your own battery whenever available.
| Advertised capacity | At 3.7 V | FAA passenger-flight band |
|---|---|---|
| 5,000 mAh | 18.5 Wh | Up to 100 Wh |
| 10,000 mAh | 37 Wh | Up to 100 Wh |
| 20,000 mAh | 74 Wh | Up to 100 Wh |
| 26,800 mAh | 99.16 Wh | Up to 100 Wh |
| 27,000 mAh | 99.9 Wh | Up to 100 Wh |
| 30,000 mAh | 111 Wh | Over 100–160 Wh: airline approval |
| 50,000 mAh | 185 Wh | Over 160 Wh: not permitted |
FAA guidance says spare lithium batteries and power banks must be in carry-on baggage. For batteries over 100 Wh through 160 Wh, obtain airline approval before travel; airlines may set stricter limits.
Worked example: 20,000 mAh at 3.7 V
Multiply 20,000 mAh by 3.7 V, then divide by 1,000. The result is 74 Wh. That falls within the FAA’s up-to-100 Wh passenger-flight band, but the power bank still belongs in carry-on baggage and the airline’s own policy still applies.
Which voltage should you enter?
Use the nominal battery or cell voltage printed with the capacity rating. Many lithium power banks rate their internal cells around 3.7 V even though the USB output is 5 V or higher. Combining the advertised cell-level mAh with the USB output voltage overstates stored energy. If the manufacturer already prints a Wh rating, use that marking as the authoritative value for travel and compare it with the calculator as a cross-check.
How to read the flight result
Under current FAA guidance, rechargeable lithium batteries from 0–100 Wh are allowed on passenger aircraft; batteries over 100 Wh through 160 Wh require air-carrier approval, and a passenger is limited to two spare batteries in that middle band. Batteries over 160 Wh are not permitted on passenger aircraft. Power banks count as spare batteries and must be carried in the cabin, not checked baggage.
This result is not permission to fly. Airlines and countries may impose tighter quantity, storage or in-flight-use rules, so check the operating airline before leaving for the airport.
Rated energy is not always delivered energy
The Wh calculation describes nominal stored energy. A power bank normally delivers less usable energy after voltage conversion, heat and cable losses. A USB power meter can help measure what a compatible device actually receives, while the manufacturer’s marked Wh rating remains the important figure for travel screening.
Sources used for assumptions: FAA PackSafe: Airline Passengers and Batteries; FAA spare lithium battery packing poster.
Frequently asked questions
How many Wh is a 20,000 mAh power bank?
At a 3.7 V nominal cell rating, 20,000 mAh equals 74 Wh: 20,000 × 3.7 ÷ 1,000. Use the voltage and Wh printed on your own power bank when available.
Can I take a 20,000 mAh power bank on a plane?
At 3.7 V it is 74 Wh, within the FAA up-to-100 Wh band. Power banks must be in carry-on baggage, and your airline may apply stricter rules, so check its current policy.
Can I take a 30,000 mAh power bank on a plane?
At 3.7 V it is 111 Wh, which is over 100 Wh. Under FAA guidance that requires advance airline approval and falls under the limit of two spare batteries in the over-100-through-160 Wh band.
What voltage should I use?
Use the nominal battery or cell voltage associated with the mAh rating, often 3.7 V for lithium power banks. Do not automatically use the 5 V USB output voltage.
Is a higher mAh always more energy?
Not necessarily — energy (Wh) depends on both mAh and voltage. A higher-voltage pack can hold more energy at the same mAh.
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