Ah to mAh: multiply by a thousand
Multiply by a thousand. A table from a 7 Ah alarm battery to a 100 Ah leisure battery, and when the comparison is worth making at all.
100 Ah is 100000 mAh. The conversion is pure arithmetic and works the same way in both directions, with nothing to assume.
The more interesting question is why two units exist for one quantity. It is readability, nothing more. A phone battery holds 0.005 Ah, which nobody writes down, so it is quoted as 5000 mAh. A car battery holds 60000 mAh, which is equally unhelpful, so it is quoted as 60 Ah. Same quantity, different convenience.
If you came here to line up two different batteries, pause for a second. Amp-hours alone will not settle it when the two run at different voltages.
Typical batteries
| Capacity | In milliamp-hours | Where you meet it |
|---|---|---|
| 7 Ah | 7000 mAh | alarm panel, UPS |
| 12 Ah | 12000 mAh | motorcycle, scooter |
| 20 Ah | 20000 mAh | small solar set |
| 45 Ah | 45000 mAh | small car |
| 100 Ah | 100000 mAh | camper, off-grid |
Amp-hours are not a measure of energy
An amp-hour describes charge, not energy. To find out what a battery will actually deliver, multiply capacity by voltage and move to watt-hours. Skip that step and you are comparing numbers that describe different things.