Weather converter
Rainfall Converter
How the rainfall converter works
US forecasts measure rain in inches; nearly everyone else uses millimeters - and one millimeter of rain is exactly one liter of water per square meter. Convert any amount below.
1 inch = 25.4 mm 1 mm = 1 L/m² 1 inch on 1 acre ≈ 102,800 litersQuick tips
- The magic equivalence: 1 mm of rain = exactly 1 liter of water per square meter.
- Rates and totals differ: 10 mm in an hour is a downpour; 10 mm across a day is just wet.
- Snow shortcut: about 10 cm of average snow melts to 1 cm of water (10:1).
Rainfall conversion chart
| mm | cm | in | L/m² |
|---|---|---|---|
| 1 | 0.1 | 0.04 | 1 |
| 2.5 | 0.25 | 0.1 | 2.5 |
| 5 | 0.5 | 0.2 | 5 |
| 10 | 1 | 0.39 | 10 |
| 25 | 2.5 | 0.98 | 25 |
| 50 | 5 | 1.97 | 50 |
| 100 | 10 | 3.94 | 100 |
| 250 | 25 | 9.84 | 250 |
Rainfall intensity classification (per hour)
| Intensity | Rate | What it looks like |
|---|---|---|
| Light rain | < 2.5 mm/h (< 0.1 in/h) | Drizzle to steady light rain |
| Moderate rain | 2.5-7.6 mm/h (0.1-0.3 in/h) | Puddles form quickly |
| Heavy rain | 7.6-50 mm/h (0.3-2 in/h) | Downpour, poor visibility |
| Violent rain | > 50 mm/h (> 2 in/h) | Tropical deluge, flash-flood risk |
Frequently asked questions
How much is 1 inch of rain in mm?
1 inch equals exactly 25.4 mm. As a soaking, one inch delivers about 25 liters of water to every square meter of ground.
Is 10 mm of rain a lot?
As a daily total, 10 mm (0.4 in) is a decent wet day but nothing extreme. As an hourly rate it qualifies as heavy rain.
How does snowfall convert to rainfall?
A common rule of thumb is 10:1 - about 10 mm of average-density snow melts down to 1 mm of water - but fluffy powder can run 20:1 and wet snow 5:1.