mAh to Wh Calculator (and Wh to mAh)
mAh to Wh converts a battery capacity in milliamp-hours into energy in watt-hours by multiplying by the voltage: Wh equals mAh times volts divided by 1000. Enter the capacity and the nominal voltage, such as 3.7 V, and a second box converts back from Wh to mAh.
18.5 Wh Wh = mAh × V ÷ 1000 → 5000 × 3.7 ÷ 1000 = 18.5 Wh (66600 J). 5000 mAh mAh = Wh × 1000 ÷ V → 18.5 × 1000 ÷ 3.7 = 5000 mAh.mAh to Wh
Wh to mAh
How to convert mAh to Wh
Capacity in mAh is charge, and watt-hours are energy. To compare batteries you need the voltage: Wh = mAh × V ÷ 1000. The conversion from mAh to coulombs is exact, 1 mAh = 3.6 C (BIPM, 2019), and 1 Wh = 3600 J, so Wh = mAh × V ÷ 1000 follows from the SI definitions.
Worked example: a 5000 mAh phone battery at 3.7 V
5000 × 3.7 ÷ 1000 = 18.5 Wh. In joules that is 18.5 × 3600 = 66 600 J.
Worked example: a power bank
A bank labeled 10 000 mAh at 3.7 V holds 37 Wh. When it charges a 5 V device the usable mAh at 5 V is smaller, 37 × 1000 ÷ 5 = 7400 mAh, before conversion losses. To turn that energy into average power over time, use the kwh to watts calculator.
mAh to Wh table
Energy for common capacities at 3.7 V, 5 V and 12 V, and the same capacity in coulombs.
| Capacity (mAh) | Wh at 3.7 V | Wh at 5 V | Wh at 12 V | Coulombs (C)×1000 |
|---|---|---|---|---|
| 1000 | 3.7 | 5 | 12 | 3.6 |
| 2000 | 7.4 | 10 | 24 | 7.2 |
| 2500 | 9.25 | 12.5 | 30 | 9 |
| 3000 | 11.1 | 15 | 36 | 10.8 |
| 3500 | 12.95 | 17.5 | 42 | 12.6 |
| 4000 | 14.8 | 20 | 48 | 14.4 |
| 5000 | 18.5 | 25 | 60 | 18 |
| 6000 | 22.2 | 30 | 72 | 21.6 |
| 10000 | 37 | 50 | 120 | 36 |
| 20000 | 74 | 100 | 240 | 72 |
| 26800 | 99.16 | 134 | 321.6 | 96.48 |
Nominal voltage
The voltage in the formula is the nominal voltage of the battery, printed on the cell or the label. Lithium-ion cells are commonly labeled around 3.6 V to 3.7 V; check your own label. Use the same voltage the capacity was measured at, or the result will be off. For the reverse step see the Wh to mAh box above, and for current conversions see milliamps to amps.
More converters are on the MicroCoulomb home page.
Frequently asked questions
How do you convert mAh to Wh?
Multiply the capacity in mAh by the voltage and divide by 1000: Wh = mAh × V ÷ 1000.
How many Wh is 10 000 mAh?
At 3.7 V it is 37 Wh. At 5 V it is 50 Wh.
How do you convert Wh to mAh?
mAh = Wh × 1000 ÷ V. 18.5 Wh at 3.7 V is 5000 mAh.
Why does the voltage matter?
Because mAh is charge and Wh is energy. The same mAh holds more energy at a higher voltage.
Updated