Rainfall Converter: mm to Inches
Most forecasts outside the US give rain in millimetres; US forecasts use inches. Enter an amount in any unit to see the others.
Formula
- inches = mm ÷ 25.4
- mm = inches × 25.4
- cm = mm ÷ 10
Millimetres are shown to 2 decimal places, centimetres and inches to 3, since a tenth of an inch is already 2.54 mm.
Reference table
| Millimetres (mm) | Centimetres (cm) | Inches (in) |
|---|---|---|
| 0.1 | 0.01 | 0.004 |
| 0.5 | 0.05 | 0.02 |
| 1 | 0.1 | 0.039 |
| 2 | 0.2 | 0.079 |
| 5 | 0.5 | 0.197 |
| 10 | 1 | 0.394 |
| 15 | 1.5 | 0.591 |
| 20 | 2 | 0.787 |
| 25.4 | 2.54 | 1 |
| 30 | 3 | 1.181 |
| 50 | 5 | 1.969 |
| 75 | 7.5 | 2.953 |
| 100 | 10 | 3.937 |
Good to know
- 1 mm of rain means a layer 1 mm deep over flat ground, which is 1 litre of water per square metre.
- Snowfall is measured differently: forecasts usually give snow depth, and melting it down yields far less liquid water, so a snow depth cannot be converted to rainfall with this factor.