Enter a watt-hour rating and a voltage to convert it into milliamp-hours, the unit most small batteries are labeled with.
How to Use the Watt-Hours to Milliamp-Hours Calculator
Enter a watt-hour rating and the cell voltage — 3.7 V is prefilled for a typical lithium-ion cell — and the milliamp-hour equivalent appears immediately.
Turning a Wh Spec Into a Number People Actually Compare
Small batteries and power banks are shopped almost entirely by mAh, so a Wh figure from a spec sheet or an airline's energy limit needs converting before it means anything next to a product listing. An 18.5 Wh energy rating at a 3.7 V nominal cell voltage converts to exactly 5,000 mAh — a genuinely common power bank capacity, which is no coincidence: manufacturers routinely quote both figures for the same product, and this is the arithmetic connecting them.
Milliamp-Hours = (Watt-Hours ÷ Voltage) × 1,000Change the voltage and the mAh answer moves with it even though the Wh figure hasn't changed at all — a reminder that mAh, on its own, is only ever half the spec. Two packs with identical Wh ratings can report very different mAh numbers if they're built around different cell voltages.