About the Rainfall Volume Calculator
Volume of water falling on any area from a given depth of rainfall.
Also known as: rain volume calculator, mm of rain to litres, rainfall on area, inches of rain volume.
How to use this calculator
- Enter area, rainfall depth, runoff coefficient.
- The result updates instantly as you type — press Calculate (or Enter) at any time.
- Review the breakdown shown under the main result.
- Use Copy result or Share to save the answer or send a link with your inputs.
Formula
litres = area (m²) × rainfall (mm) × runoff coefficient
Worked example
Using the values pre-filled in the calculator above:
- Area = 500 m²
- Rainfall depth = 25 mm
- Runoff coefficient = 1
the calculator returns:
- Water volume: 12,500 litres
- In cubic metres: 12.5
- In US gallons: 3,302
- Weight of the water: 12,500 kg