About this tool
Battery Capacity Converter is a free, in-browser tool that converts battery capacity between milliamp-hours (mAh) and watt-hours (Wh) using the pack's nominal voltage. Pick a direction, enter the capacity and the nominal voltage, and it returns the converted value plus the equivalent in kilowatt-hours. All math is local; nothing is uploaded.
Capacity in mAh is a charge rating and only becomes energy once you include voltage. The conversions are Wh = mAh × V ⁄ 1000 and mAh = Wh × 1000 ⁄ V, where V is the nominal voltage. Dividing or multiplying by 1000 converts between milliamp-hours and amp-hours. Kilowatt-hours are simply watt-hours ⁄ 1000.
Use it to compare batteries rated in different units, check an airline's 100 Wh carry-on limit for a power bank, or convert a pack's mAh label into usable energy. A 3000 mAh cell at 3.7 V holds 11.1 Wh; the same 3000 mAh at 3.85 V holds slightly more, which is why voltage matters.