mAh vs Wh: how to actually compare battery sizes
Why you can't compare mAh across devices — and the one number that lets you.
By the Let’s Compare Editorial Team · 1 min read · Updated September 21, 2026
Phone batteries are quoted in mAh, while laptop and handheld batteries use Wh — and the two aren't directly comparable. Here's what each means and how to compare battery sizes honestly.
mAh vs Wh
| mAh | Wh | |
|---|---|---|
| Measures | Charge | Energy |
| Depends on voltage? | No (charge only) | Yes (energy) |
| Compare across devices? | No | Yes |
| Convert | — | mAh × V ÷ 1000 |
What mAh and Wh mean
mAh (milliamp-hours) measures electrical charge — how much current a battery can supply over time. But charge alone doesn't tell you energy, because energy also depends on voltage. Wh (watt-hours) measures actual energy, and it's the fairer number: watt-hours = amp-hours × voltage. A 5,000 mAh cell at 3.8 V holds about 19 Wh.
Why you can't compare mAh across devices
Because voltage varies. A phone battery runs around 3.7–3.8 V; a laptop battery might be 11–15 V. So a laptop's '6,000 mAh' holds far more energy than a phone's '6,000 mAh', because each mAh is delivered at a higher voltage. Comparing mAh between a phone and a laptop is meaningless — you'd be comparing charge, not energy.
How to compare honestly
Convert to watt-hours. If a battery lists mAh and voltage, multiply them and divide by 1,000 to get Wh (e.g. 5,000 mAh × 3.8 V ÷ 1,000 = 19 Wh). Then any two batteries sit on the same scale. And remember capacity isn't battery life: an efficient chip and screen can outlast a bigger battery that's feeding hungry hardware.
Sources & further reading
This article is original analysis grounded in independently verified references, including non-English outlets. The facts above are sourced so you can check them yourself.
- Ampere-hour (charge, not energy) — Wikipedia
- Kilowatt-hour (energy = charge × voltage) — Wikipedia