Rainfall Converter
Convert rainfall measurements between millimeters, inches, liters per square meter, and more. Free online precipitation converter for meteorology, hydrology, and agriculture.
Understanding Rainfall Measurements
Rainfall measures precipitation depth over a specific period. Measurements use millimeters or inches. One millimeter of rain equals one liter per square meter. Rainfall data helps with flood prediction, agriculture planning, and water resource management.
Rain gauges collect and measure precipitation. Standard gauges measure depth directly. Tipping bucket gauges count tips to calculate volume. Weather radar estimates rainfall over large areas.
Rainfall Intensity Classifications
| Intensity | mm/hour | inches/hour | Description |
|---|---|---|---|
| Very Light | Less than 0.25 | Less than 0.01 | Barely perceptible |
| Light | 0.25 - 1.0 | 0.01 - 0.04 | Gentle rain |
| Moderate | 1.0 - 4.0 | 0.04 - 0.16 | Steady rain |
| Heavy | 4.0 - 16.0 | 0.16 - 0.63 | Downpour |
| Very Heavy | 16.0 - 50.0 | 0.63 - 1.97 | Torrential rain |
| Extreme | More than 50.0 | More than 1.97 | Flash flood risk |
Rainfall Conversion Formulas
Convert between rainfall units using these formulas.
Example: Converting 2 inches of rainfall to millimeters and liters per square meter
Annual Rainfall Averages by Region
| Location | Annual Rainfall (mm) | Annual Rainfall (inches) | Climate Type |
|---|---|---|---|
| Mawsynram, India | 11,871 | 467 | Tropical monsoon |
| Singapore | 2,345 | 92 | Tropical rainforest |
| London, UK | 601 | 24 | Temperate oceanic |
| New York, USA | 1,268 | 50 | Humid subtropical |
| Sydney, Australia | 1,213 | 48 | Humid subtropical |
| Cairo, Egypt | 25 | 1 | Desert |
| Seattle, USA | 952 | 37 | Oceanic |
| Tokyo, Japan | 1,530 | 60 | Humid subtropical |
Water Volume from Rainfall
- 1 mm of rain on 1 hectare = 10,000 liters of water
- 1 inch of rain on 1 acre = 27,154 gallons of water
- 1 mm of rain on 1 m² = 1 liter of water
- 1 inch of rain on 1,000 ft² = 623 gallons of water
- Rainwater harvesting potential depends on roof area and local rainfall
Frequently Asked Questions
What does 1 mm of rain mean?
One millimeter of rain means water would cover a flat surface to a depth of 1 mm if none drained away. This equals 1 liter of water per square meter of ground area.
How is rainfall measured?
Rain gauges collect precipitation in a calibrated cylinder. Manual gauges require reading after each event. Automatic gauges transmit data continuously. Weather radar estimates rainfall over wide areas.
What is considered heavy rainfall?
Rainfall exceeding 4 mm per hour qualifies as heavy. Rainfall over 16 mm per hour indicates very heavy rain with flash flood potential. Intensity matters more than total accumulation for flooding.
How do I calculate rainwater collection from my roof?
Multiply roof area in square meters by rainfall in millimeters. Result equals liters of collectable water. For a 100 m² roof with 50 mm rain: 100 × 50 = 5,000 liters potential collection.
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