Calculate watt hours from amp hours, or amp hours from watt hours, using your battery voltage, with support for mAh and kWh.
Common Mistakes Quick tips
- Entering values in both fields. Fill exactly one: either Amp-hours or Watts.
- Leaving out voltage or time; both are required to relate Ah and W.
- Confusing Watts (W) with watt-hours (Wh), or Amp-hours (Ah) with amps (A).
- Mixing mAh and Ah without converting (1 Ah = 1000 mAh).
- Assuming peak power instead of average power; this conversion gives average power over the specified time and assumes roughly constant voltage.
When to Use This Calculator
- Estimating average load (W) a battery can supply over a target runtime.
- Finding required battery capacity (Ah) for a device with known power draw and runtime.
- Converting between energy (Wh), capacity (Ah), and power (W) using the battery’s voltage.
Input Definitions
- Voltage (V) — enter in V, kV, or mV.
- Time (t) — duration in hours, minutes, seconds, or days (converted to hours).
- Amp-hours (Ah) — battery capacity; mAh is supported (1 Ah = 1000 mAh).
- Watts (W) — average power over the entered time.
- Conversions — Wh = Ah × V; W = (Ah × V) ÷ t; Ah = (W × t) ÷ V.
Customize This Calculator
Build your own version. Describe what you want changed, added, or compared.
- All Unit Converters
- Amp Hours to Watt Hours Calculator
- Amp Hours To Milliamp Hours Converter Calculator
- Ah to Kwh Conversion Calculator
- Ampere to Coulomb Per Second Conversion Calculator
Amp Hours to Watt Hours Formula
Wh = Ah * V
Ah = Wh / V
To convert amp hours to watt hours, multiply the capacity in amp hours by the battery voltage. To convert in the other direction, divide the energy in watt hours by the voltage.
Where:
- Wh is the energy in watt hours.
- Ah is the charge or capacity in amp hours.
- V is the voltage in volts.
If your capacity is given in milliamp hours (mAh), divide it by 1000 to get amp hours first, because 1 Ah equals 1000 mAh. To express the energy in kilowatt hours (kWh), divide the watt hours by 1000.
Reference Values
The table shows the watt hours you get for common battery capacities and voltages.
| Capacity | Voltage | Energy (Wh) |
|---|---|---|
| 50 Ah | 12 V | 600 Wh |
| 100 Ah | 12 V | 1200 Wh |
| 100 Ah | 24 V | 2400 Wh |
| 200 Ah | 48 V | 9600 Wh |
| 3000 mAh | 3.7 V | 11.1 Wh |
Example Problems
Example 1. You have a 100 Ah battery rated at 12 V. Multiply the capacity by the voltage: 100 Ah times 12 V equals 1200 Wh, which is also 1.2 kWh.
Example 2. You have a 500 Wh power station running at 24 V and want the capacity in amp hours. Divide the energy by the voltage: 500 Wh divided by 24 V equals about 20.83 Ah.
Frequently Asked Questions
Do you need the voltage to convert amp hours to watt hours? Yes. Amp hours measure charge and watt hours measure energy, so you must know the voltage to move between them. Without voltage the conversion cannot be done.
How do you convert milliamp hours to watt hours? Multiply the milliamp hours by the voltage, then divide by 1000. For example, a 3000 mAh battery at 3.7 V holds 3000 times 3.7 divided by 1000, which equals 11.1 Wh.
Is an amp hour the same as a watt hour? No. An amp hour describes how much charge a battery can deliver, while a watt hour describes how much energy it stores. They are equal in number only when the voltage is exactly 1 V.
