Rainfall Volume Calculator

All misc tools

Calculate volume of rainfall over an area.

Catchment Area

Surface Area (m²)

Rainfall Depth (mm)

To convert Square Feet to Square Meters, multiply by 0.0929. To convert Inches to MM, multiply by 25.4.

Water Collected

Total Volume1,000 L

264.2 Gallons

200L Rain Barrels5.0Standard container equivalent

This volume represents the total theoretical catch. Actual collection efficiency (runoff coefficient) is usually 80-95% for most roofs.

About this calculator

Overview

Rainfall volume calculation determines water volume from rainfall over specific area. Essential for drainage design, rainwater harvesting, and flood planning.

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Pro Tips

1 inch rain = 0.62 gallons per sq ft.
Roof collection: Area × Rain × 0.62.
1% slope minimum for drainage.
First flush diverts dirty water.

Fun Facts

"1 inch rain on 1,000 sq ft = 623 gallons."
"Average US rainfall: 30 inches/year."
"Rainwater harvesting: 50% efficiency typical."
"100-year flood: 1% annual probability."

Formula: Volume = Area × Rainfall Depth; 1 inch rain on 1 acre = 27,154 gallons