Battery capacity & energy converter
Choose the units on your battery label and the units you need. Results update as you type. To convert between mAh or Ah and Wh or kWh, enter the nominal battery voltage too.
10,000 mAh at 3.7 volts equals 37 Wh.
10,000 mAh at 3.7 V
Nominal stored energy
10,000 ÷ 1,000 × 3.7 = 37 Wh
- mAh
- 10,000
- Ah
- 10
- Wh
- 37
- kWh
- 0.037
These values describe the same battery rating at 3.7 V. We round the displayed values but keep the full result when you reverse the conversion.
A 10,000 mAh rating at 3.7 V is 37 Wh. At 7.4 V, the same charge capacity is 74 Wh. Check the battery label before changing the voltage.
Compare two battery labelsUse watt-hours to compare batteries at different voltages.
Understand the conversion
Which units are on your battery label?
mAh and Ah measure electric charge. Wh and kWh measure energy. Voltage connects the two: a 10 Ah battery rated at 12 V stores 120 Wh of nominal energy; a 10 Ah battery rated at 24 V stores 240 Wh.
Converting mAh to Ah or Wh to kWh only changes the scale. Neither conversion needs voltage. Choose either direction in the From and Convert to menus, or select Reverse conversion to use the result as your next input.
Formula and worked example
Ah = mAh ÷ 1,000
kWh = Wh ÷ 1,000
Wh = Ah × V
Ah = Wh ÷ V
10,000 mAh is 10 Ah. At a nominal 3.7 V, that is 37 Wh or 0.037 kWh.
The NIST conversion reference lists ampere-hours under electric charge and watt-hours under energy. The battery calculations here use nominal label voltage.
Battery labels at different voltages
These examples keep the 10 Ah charge rating fixed while changing nominal voltage. This reference table stays fixed while you edit the calculator.
| mAh | Nominal voltage | Wh |
|---|---|---|
| 10,000 | 3.2 V | 32 |
| 10,000 | 3.7 V | 37 |
| 10,000 | 12 V | 120 |
| 10,000 | 12.8 V | 128 |
| 10,000 | 24 V | 240 |
| 10,000 | 48 V | 480 |
Common questions
Which voltage should I use?
Use the nominal voltage printed with the capacity rating. For a pack rating, use the pack voltage. For a single cell, use the cell voltage. A charger's full-charge voltage or a USB port's output voltage may describe a different part of the system.
Can this convert watts or amps?
This converter handles capacity and energy. Watts measure power; amps measure current. Turning either into an energy or capacity figure also needs a duration. Use the runtime tool when you know the load and want a time estimate.
Does nominal energy equal usable energy?
Usable energy depends on discharge current, temperature, battery condition, cutoff voltage, and conversion losses. This tool converts label ratings; it does not measure how much energy reaches a device.