Enter an amp-hour capacity and a voltage to convert it directly into watt-hours, the more universal battery energy unit.
How to Use the Amp-Hours to Watt-Hours Calculator
Enter an amp-hour capacity and set the voltage field to match the battery's nominal rating — 12 V loads by default. The watt-hour result updates as soon as either field changes.
Watt-Hours Are the Number That Actually Gets Compared
Amp-hours only mean something once a voltage is attached, which is exactly why manufacturers, retailers, and airlines increasingly print Wh on batteries instead of — or alongside — Ah. A carry-on lithium battery limit, for instance, is written in watt-hours precisely because Ah alone can't tell a security screener how much energy is actually in the pack.
Energy (Wh) = Amp-Hours × VoltageA 100 Ah car battery at 12 V works out to 1,200 Wh. An e-bike battery rated at a much smaller-looking 20 Ah but built around a 48 V pack comes out to 960 Wh — nearly the same energy content as the car battery, from an amp-hour number that's a fifth the size. Comparing the two Ah ratings directly would suggest the car battery holds five times more energy; comparing the Wh figures shows they're nearly even. That gap is the entire reason this conversion exists.