Watt-Hours to Amp-Hours Calculator
Converts between watt-hours and amp-hours at a given voltage. Batteries are sold in amp-hours and loads are rated in watts, so this is the conversion that stands between a spec sheet and an answer.
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The formula
Wh = Ah × V · Ah = Wh ÷ V
Amp-hours measure charge, not energy. Multiplying by the pack voltage converts charge into energy, which is the only figure comparable between systems of different voltages.
What to watch out for
The distinction matters more than it looks:
- Amp-hours are charge; watt-hours are energy. A 100 Ah battery at 12 V holds 1,200 Wh. A 100 Ah battery at 48 V holds 4,800 Wh — four times the energy, same headline number.
- Compare packs in watt-hours, always. It is the only figure that is voltage-independent, which is why EV and laptop batteries are quoted that way.
- Nominal voltage, not resting voltage. Use 12 V for a lead-acid 12 V pack even though it sits at 12.7 V charged; the nominal figure is what capacity ratings assume.
Frequently Asked Questions
How many amp-hours is 1000 Wh?
83.3 Ah at 12 V, 41.7 Ah at 24 V, or 20.8 Ah at 48 V. The answer depends entirely on the voltage.
Why do batteries use amp-hours at all?
Historical convention, and because charge is what a coulomb counter measures directly. It is a poor unit for comparing packs, which is why watt-hours have taken over in consumer electronics.
Is a 100 Ah battery twice as good as a 50 Ah one?
Only at the same voltage and chemistry. A 50 Ah lithium pack usable to 90% depth of discharge delivers more real energy than a 100 Ah lead-acid pack usable to 50%.