Amp Hours to Watt Hours Calculator
Battery capacity is often written in amp-hours, but energy is measured in watt-hours. Multiplying amp-hours by voltage converts one into the other. This page does that step for any battery.
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- Saves on this device
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How it works
Watt-hours equal amp-hours times volts. For a battery at 12 volts, the watt-hours are the amp-hour rating times 12, and dividing by 1,000 gives kilowatt-hours.
Use the nominal voltage on the label. The real voltage moves as a battery charges and drains, so the result is an approximation.
Worked example
A battery of 100 amp-hours at 12 volts holds 1,200 watt-hours, or 1.2 kilowatt-hours.
Questions
Why do batteries use amp-hours at all?
Amp-hours describe charge, which is simple to measure. Watt-hours describe energy, which is what matters when batteries of different voltages are compared.
Which voltage should I use?
The nominal voltage is the usual choice for a rough figure. Use the voltage printed on the label or in the data sheet.
Can I compare two batteries with different voltages?
Yes. Convert both to watt-hours, and the one with the bigger number holds more energy.
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