mAh to Wh converter
Wh = mAh × volts ÷ 1,000. A 10,000 mAh power bank at 3.7 V holds 37 Wh. Type in either box to convert both ways.
Not sure? Use the voltage printed on the battery. If there's none and it's a phone or power bank, 3.7 V is the usual value, not the 5 V of the USB port.
10,000 mAh × 3.7 V ÷ 1,000 = 37 Wh.
Through a 5 V USB port this delivers about 6,290–6,660 mAh after conversion loss.
Flying (FAA): up to 100 Wh is allowed on passenger aircraft. Spare batteries and power banks go in carry-on bags only.
Use the Wh printed on the battery if it has one, and check the FAA rules and your airline before flying: airlines can be stricter.
mAh to Wh conversion table (3.7 V)
| Capacity | Energy at 3.7 V | FAA band |
|---|---|---|
| 1,000 mAh | 3.7 Wh | Allowed |
| 2,000 mAh | 7.4 Wh | Allowed |
| 3,000 mAh | 11.1 Wh | Allowed |
| 5,000 mAh | 18.5 Wh | Allowed |
| 10,000 mAh | 37 Wh | Allowed |
| 15,000 mAh | 55.5 Wh | Allowed |
| 20,000 mAh | 74 Wh | Allowed |
| 27,000 mAh | 99.9 Wh | Allowed |
| 30,000 mAh | 111 Wh | Airline approval |
| 50,000 mAh | 185 Wh | Forbidden |
Wh to mAh conversion table
| Energy | At 3.7 V | At 5 V | At 11.1 V |
|---|---|---|---|
| 10 Wh | 2,703 mAh | 2,000 mAh | 901 mAh |
| 22.2 Wh | 6,000 mAh | 4,440 mAh | 2,000 mAh |
| 50 Wh | 13,514 mAh | 10,000 mAh | 4,505 mAh |
| 74 Wh | 20,000 mAh | 14,800 mAh | 6,667 mAh |
| 99 Wh | 26,757 mAh | 19,800 mAh | 8,919 mAh |
| 100 Wh | 27,027 mAh | 20,000 mAh | 9,009 mAh |
| 160 Wh | 43,243 mAh | 32,000 mAh | 14,414 mAh |
| 300 Wh | 81,081 mAh | 60,000 mAh | 27,027 mAh |
| 1,000 Wh | 270,270 mAh | 200,000 mAh | 90,090 mAh |
Which voltage should I use?
The same mAh number means different amounts of energy at different voltages, so the voltage decides the answer. That's why a conversion without a voltage isn't possible.
- Phones and power banks: the mAh on the label refers to the battery cells. Most lithium-ion cells have a nominal voltage of 3.7 V, so use that, unless the label says otherwise. Some phones state a slightly higher value; pick "Other" and enter it.
- USB output: USB charging runs at 5 V. The cells' energy is stepped up to reach it, so the same battery shows fewer mAh at 5 V. Anker's example: 37 Wh ÷ 5 V = 7,400 mAh, before the 85–90% converter efficiency it quotes. Some labels call the result "rated capacity".
- Laptops, drones, camera packs: these stack cells in series. Use the voltage printed on the pack.
- 12 V and bigger batteries: use the system voltage. These are usually rated in Ah, so the battery runtime calculator is the better tool.
Airline limits in watt-hours
The FAA sets limits in Wh, not mAh, which is why a power bank's Wh figure matters when you fly. From the FAA's PackSafe page:
| Battery size | Passenger aircraft (FAA) |
|---|---|
| Up to 100 Wh | Allowed |
| 101–160 Wh | Needs air carrier approval, at most two spares per person |
| Above 160 Wh | Forbidden |
Spare batteries and power banks must be in your carry-on, never in checked bags. Many airlines set stricter limits, so this table doesn't replace asking yours. Rules differ outside the US.
Questions
How do I calculate Wh from mAh?
Divide mAh by 1,000 to get Ah, then multiply by the voltage. For 20,000 mAh at 3.7 V: 20 Ah × 3.7 V = 74 Wh.
How do I convert Wh to mAh?
Multiply Wh by 1,000 and divide by the voltage. For 50 Wh at 3.7 V: 50 × 1,000 ÷ 3.7 = about 13,514 mAh.
How many watts is a given mAh?
mAh can't be converted to watts directly, because watts measure power and mAh measures stored charge. Convert to Wh first, then divide by the hours: a 5,000 mAh battery at 3.7 V holds 18.5 Wh, which is 18.5 W for one hour or 9.25 W for two.
How many mAh is 100 Wh?
About 27,027 mAh at 3.7 V. That's why power banks meant for flying usually stay below about 27,000 mAh (99.9 Wh at 3.7 V).
Why does my 10,000 mAh power bank deliver less than 10,000 mAh?
The 10,000 mAh is measured at the cells' 3.7 V, while USB runs at 5 V, and the step-up loses energy on top. Anker puts the conversion at 85–90% efficient, so about 6,290–6,660 mAh arrive at 5 V.
What if I need more than 160 Wh?
That's portable power station territory, for road trips rather than flights. See the power station comparison, or size one for your devices with the power station calculator. Device-by-device numbers are in the guides for a phone and a laptop.
Sources: FAA PackSafe (formula and limits), Anker (3.7 V cells, 5 V USB, converter efficiency). More on our method page.