Power bank mAh to Wh calculator
Type the mAh printed on your power bank to get its watt-hours (Wh) and see whether it is under the 100 Wh limit for flights. The page shows an example result even without JavaScript.
Quick answer
Wh = mAh × V ÷ 1,000. Use the cell voltage, about 3.6 to 3.7 V, not 5 V. A 20,000 mAh power bank is 74 Wh, which is under the 100 Wh limit. At 3.7 V the limit is about 27,027 mAh. If the pack prints a Wh figure, trust that. For the full flight rules, read our power bank rules page.
Convert mAh to Wh
74 Wh at 3.7 V
Under 100 Wh. Even at 3.85 V it is 77 Wh, so it is within the normal 100 Wh limit.
If you used 5 V by mistake you would get 100 Wh, which overstates the energy by about 35 per cent.
Common sizes at 3.7 V
| Power bank | Wh | Under 100 Wh? |
|---|---|---|
| 5,000 mAh | 18.5 | Yes |
| 10,000 mAh | 37 | Yes |
| 20,000 mAh | 74 | Yes |
| 26,800 mAh | 99.2 | Close, check the printed Wh |
| 30,000 mAh | 111 | No |
| 40,000 mAh | 148 | No |
At 3.7 V the 100 Wh limit is about 27,027 mAh. Limit = 100 Wh.
The formula
Wh = mAh × V ÷ 1,000
The US aviation regulator, the FAA, gives the same rule: watt-hours equal the battery’s voltage times its amp-hours, and amp-hours are mAh divided by 1,000.
Why the voltage is not 5 V
A power bank stores energy in lithium-ion cells. Battery University lists the nominal voltage of common lithium-ion cells as about 3.6 to 3.7 V per cell. The USB port shows 5 V because a circuit inside raises the cell voltage. That does not add energy, so the Wh of the pack is set by the cell voltage.
We check 3.6 V, 3.7 V and 3.85 V. The first two are the typical nominal values. We use 3.85 V as a cautious high end for newer cells, which is our own safety margin and not a figure from a standard. A pack counts as under 100 Wh here only if it stays under even at 3.85 V. Cells with a lower voltage, such as lithium iron phosphate at about 3.2 V, hold less energy than this estimate.
Some packs print a capacity measured at the USB output instead of the cell, so the number can look smaller. If the pack prints Wh, that figure beats any conversion.
The 100 Wh limit on flights
Airlines use Wh, not mAh. Under IATA’s guidance of 31 March 2026, a power bank above 100 Wh is not allowed on a flight and each passenger may carry two. India’s DGCA circular 01/2025 also says to carry power banks in hand baggage only and not to use or charge them in flight. Our power bank rules for Indian flights page explains what each source says and what the airlines publish. Airlines can be stricter, so check yours.
Frequently asked questions
How do I convert mAh to Wh?
Multiply the mAh by the cell voltage and divide by 1,000. A 20,000 mAh power bank at 3.7 V is 20,000 × 3.7 ÷ 1,000 = 74 Wh.
Why not use 5 V?
Because 5 V is what the USB port outputs, not what the cells store. The energy sits in the lithium-ion cells at about 3.6 to 3.7 V, and a circuit steps it up to 5 V or more. Using 5 V overstates the energy by about a third.
Is a 20,000 mAh power bank allowed on a flight?
Normally yes: it is about 74 Wh, below 100 Wh. Keep it in hand baggage, do not use or charge it in flight, and carry no more than two.
Is a 30,000 mAh power bank allowed on a flight?
At 3.7 V it is 111 Wh, which is over 100 Wh. IATA’s March 2026 guidance does not allow a power bank above 100 Wh. A pack printed with a Wh figure under 100 would be fine, so read the label.
What if my power bank shows no Wh?
Work it out here, and if the result is close to 100 Wh or the pack shows no clear capacity, leave it at home. Akasa Air lists power banks without a clear capacity label among batteries not to travel with.
Sources
Checked on 14 October 2026. Rules and tariffs change, so confirm with the official page.