Rainfall Converter: Convert mm, Inches, cm and L/m²
Turn rain depth into a useful amount: Convert rainfall between millimeters, inches, centimeters and liters per square meter, with intensity classifications and reference storms.
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How much water falls over an area?
Water delivered2,540 litersabout 671 US gallons
25.4 mm over 100 m² delivers 2,540 liters. Whether that is disruptive depends on how quickly it falls and how the surface drains.
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 |
Rain depth, rainfall rate and collected water are different answers
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.
For the evidence, limits and practical use behind this result, read How Rainfall Is Measured. The weather tools guide explains when each calculator is the right one.
1 inch = 25.4 mm1 mm = 1 L/m²1 inch on 1 acre ≈ 102,800 liters
Use rainfall totals without losing context
- 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 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 |
Rain depth, rate and snowfall 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.