How to Calculate Rainwater Harvested from Your Roof

Calculating potential rainwater capture is straightforward: multiply roof length by width to get square footage. Multiply that by inches of rainfall. Multiply the result by 0.623 (the conversion factor) to get gallons. For a 1,000 sq. ft. roof, one inch of rain yields about 623 gallons. Atlanta averages 50 inches annually—roughly 31,000 gallons on that roof—though most falls in spring and fall, not summer when plants need it most. For a detailed guide on harvesting and storage, see https://xrl.us/RAINHARVEST.