What this converter does
This converter turns milliampere-hours into watt-hours and back. Since energy equals charge times voltage, enter the battery voltage — 3.7 V by default for lithium. Type a value and read the result as you type.
Converting a phone or power-bank mAh rating to Wh is what airlines and shippers need for their 100 Wh carry-on limit.
The units it covers
Energy (Wh) and charge (mAh) are linked by the battery voltage — energy is charge times voltage.
View all units & their values
| Unit | Symbol | Value | Mainly used |
|---|---|---|---|
| Watt-hour | Wh | energy | Battery/pack energy capacity |
| Milliampere-hour | mAh | charge | Cell/phone battery rating |
| Voltage | V | input | Nominal battery voltage |
The formula
Energy equals charge times voltage, so watt-hours and milliampere-hours are related through the pack voltage:
Wh = mAh × V ÷ 1000Where:
- Wh = energy in watt-hours
- mAh = charge in milliampere-hours
- V = nominal battery voltage
Worked example
Convert 20,000 mAh at 3.7 V to Wh.
Wh = mAh × V ÷ 100020,000 × 3.7 ÷ 1000 = 74 WhSo a 20,000 mAh power bank at 3.7 V is 74 Wh — under the 100 Wh flight limit.
The units in this example
A unit of electric charge — how phone and cell batteries are usually rated. Only comparable at the same voltage.
- 1,000 mAh = 1 Ah
- Wh = mAh × V ÷ 1000
- 20,000 mAh @3.7V = 74 Wh
- mAh = Wh × 1000 ÷ V
A unit of energy — the true capacity of a battery, independent of voltage. Airlines rate packs in Wh.
- 1 Wh = 1,000 mWh
- 1 Wh = 0.001 kWh
- Wh = mAh × V ÷ 1000
- 100 Wh flight limit