Rainfall Volume Calculator
Calculate total water volume from rainfall on a given area.
Useful for rainwater harvesting, irrigation, and drainage planning.
Water Volume
Rainfall volume tells you how much water falls on a given area. This is essential for rainwater harvesting, drainage design, and irrigation.
Volume = Rainfall Depth × Area
In imperial units:
- 1 inch of rain on 1 sq ft = 0.623 gallons
- 1 inch of rain on 1,000 sq ft = 623 gallons
- 1 inch of rain on 1 acre = 27,154 gallons
In metric units:
- 1 mm of rain on 1 sq m = 1 liter
- 10 mm of rain on 100 sq m = 1,000 liters (1 cubic meter)
Typical roof collection efficiency is about 80–90%. Not all rain reaches your collection barrel due to evaporation and splashing.