Rainfall Volume Calculator
Convert millimetres or inches of rain on an area into litres or gallons.
About the Rainfall Volume Calculator
Enter the rainfall depth and the area it falls on, in metric or imperial units. The calculator gives the volume of water in litres, cubic metres and gallons, and its weight.
Rainfall depth times area gives volume: 1 mm on 1 m² is exactly 1 litre, and 1 mm on a hectare is 10 m³ (10,000 L). One inch of rain on an acre is about 27,154 US gallons, weighing over 100 tonnes.
The formula
Litres = rainfall (mm) × area (m²)
Worked example
25 inches of rain over 1 acre
- 1 inch on an acre is about 102.8 m³
- 25 inches: 2,569.8 m³ = 2,569,754 litres
- About 678,857 US gallons, weighing 2,570 tonnes
Questions people ask
How much is an inch of rain on an acre?
About 27,154 US gallons (102.8 m³).
Does all of it run off?
No, much soaks in or evaporates, depending on surface and soil.