mAh, Ah & Wh Converter

Convert battery capacity between milliamp-hours, amp-hours and watt-hours, using the battery's nominal voltage.

Amp-hours (Ah) and milliamp-hours (mAh) only make sense at a given voltage. Watt-hours (Wh) include the voltage, so they let you compare a phone power bank, a cordless tool pack and a 12V battery fairly. Watt-hours = Amp-hours × Volts.

1. Your battery

Use the capacity and nominal voltage from the label or manual.

Common: 3.6–3.7V lithium-ion cell or power bank, 3.2V LiFePO4 cell, 12V lead-acid or AGM, 12.8V LiFePO4, 18V or 36V tool packs.

2. Results

How it was worked out

    What this does and doesn't tell you

    • This converts the rated capacity. The energy you can actually use is lower. It depends on the chemistry, the recommended depth of discharge, temperature, age and how fast you draw it.
    • Power banks are rated at the internal cell voltage (usually 3.6V or 3.7V), not the 5V USB output. After conversion losses, you get noticeably fewer mAh out at 5V than the label says.
    • Airlines set lithium battery limits in watt-hours. Check your airline's rules before you fly.
    • Damaged, swollen or overheating lithium batteries can catch fire. Stop using them and dispose of them through a battery recycling drop-off.

    Next steps

    Compare battery types in LiFePO4 vs AGM: Which Battery Lasts Longer?. To see how long a battery will run a load, use the Battery Runtime Calculator on Wired For The Wild. To go from watts to amps, use the Watts, Amps & Volts Calculator.

    Technical note: This is general educational information, not a substitute for a design calculation, manufacturer instructions or applicable Australian standards. Everything is worked out in your browser. Nothing is saved or sent anywhere.

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