Amp Hours to Watt Hours Converter

Multiply amp-hours by the battery's nominal voltage: watt-hours equal amp-hours times volts (Wh = Ah x V). For example, a 100 Ah battery at 12 V holds 100 x 12 = 1,200 Wh, or 1.2 kWh. To go the other way, divide watt-hours by volts to get amp-hours (Ah = Wh / V).

Amp-hours measure charge capacity, while watt-hours measure energy, and voltage is what links them. The same 100 Ah rating is 1,200 Wh at 12 V but 2,400 Wh at 24 V, so the energy depends entirely on the pack voltage. Always use the nominal voltage printed on the battery, not the fully charged or fully discharged voltage.

Use the nominal (rated) voltage, which is the average voltage over a discharge. Common values are 3.7 V for a single lithium-ion cell, 12 V for car, RV, and marine batteries, 24 V or 48 V for solar and home storage, and 36 V for many e-bikes. The converter includes a preset menu for these so you do not have to remember them.

Nameplate watt-hours are the theoretical maximum if you drained the battery to zero with no losses, which you rarely do. You lose capacity to depth-of-discharge limits (lead-acid is often kept above 50%, lithium can use 80 to 100%) and to inverter and charging inefficiency (typically 85 to 95%). The usable estimate multiplies the nameplate Wh by your depth of discharge and efficiency to give a more realistic planning number.

They measure the same thing at different scales: 1 amp-hour equals 1,000 milliamp-hours. Phone and small-device batteries are usually labeled in mAh, while car, RV, and solar batteries use Ah. A 2,000 mAh phone cell is 2 Ah, and at 3.7 V that is about 7.4 Wh.

Yes, and watt-hours are the fair way to do it. Amp-hours alone are misleading because a 100 Ah 12 V battery (1,200 Wh) holds the same energy as a 50 Ah 24 V battery (1,200 Wh). Convert both to watt-hours or kilowatt-hours first, then compare those numbers to see which actually stores more energy.