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Battery Capacity Calculator

Convert amp-hours and voltage to watt-hours to compare batteries of any voltage on equal terms.

Energy capacity
1,200 Wh
100 Ah × 12 V = 1,200 Wh. Use watt-hours to compare batteries of different voltages on equal footing.
Kilowatt-hours
1.2 kWh
Milliamp-hours
100,000 mAh

How it works

  1. 1Enter the battery’s rated capacity in amp-hours (Ah) from the label or datasheet.
  2. 2Enter the nominal battery voltage in volts (e.g. 12 V or 3.7 V).
  3. 3The calculator multiplies Ah × V to give watt-hours, plus kWh and mAh equivalents.

Use cases

  • Sizing an off-grid solar battery bank by comparing packs in Wh.
  • Estimating EV or e-bike range from the pack energy in kWh.
  • Checking if a power station can run an appliance for a target time.

Frequently asked questions

Why use watt-hours instead of amp-hours?

Amp-hours only describe capacity at one voltage. A 100 Ah 12 V battery holds 1200 Wh, while a 100 Ah 24 V battery holds 2400 Wh. Watt-hours let you compare any two batteries directly.

How is the watt-hour figure calculated?

Wh = Ah × V. For example, 100 Ah × 12 V = 1200 Wh = 1.2 kWh — a direct multiplication.

What is the difference between Wh and kWh?

1 kWh = 1000 Wh. Kilowatt-hours appear on electricity bills and large packs (EVs, home storage); the tool shows both units.

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