Calculate rainfall volume from rainfall depth and area. Estimate gallons of rain, cubic feet, cubic yards, acre-inches, runoff, roof collection, water captured, water lost, and rainfall totals for gardens, roofs, yards, fields, ponds, and drainage planning.
Rainfall from area:
The calculator converts rainfall depth and land area into water volume in gallons, cubic feet, cubic yards, liters, and acre-inches.
Roof collection:
Enter roof area and collection efficiency to estimate how much rainwater can be captured in barrels, tanks, or cisterns.
Runoff estimate:
Enter a runoff coefficient to estimate how much rainfall may become surface runoff instead of soaking into the ground.
Known volume conversion:
Enter an existing water volume to convert between gallons, cubic feet, cubic yards, liters, cubic meters, and acre-inches.
A rainfall calculator helps estimate how much water falls on a roof, yard, garden, field, pond, or drainage area during a rain event.
It can be useful for rain barrels, irrigation planning, drainage, runoff estimates, garden watering, stormwater projects, pond filling, roof collection systems, and water conservation planning.
Your result shows total rainfall volume, collected water, runoff water, absorbed water, gallons, cubic feet, cubic yards, liters, cubic meters, acre-inches, rain barrels needed, and estimated water value. These are planning estimates based on rainfall depth, area, efficiency, and runoff settings.
Multiply rainfall depth by area. For example, 1 inch of rain over 1 square foot equals about 0.623 gallons of water.
One inch of rain on one acre is about 27,154 gallons of water.
Multiply roof area by rainfall depth, convert to gallons, then multiply by your collection efficiency to account for gutter and system losses.
A runoff coefficient estimates the percentage of rainfall that becomes surface runoff instead of soaking into the ground or being captured.