Rainwater Collection Calculator

Rainwater Collection Calculation Formulas and Equations

Roof Area (ft2) X Precipitation Amount (in) X 0.623 = Amount Collected (gallons)

Easy Formula to Remember:   1″ of Rain on 1,000 sf  Roof Will Yield 623 Gallons

Roof Area (m2) X Precipitation Amount (mm) = Amount Collected (liters)

Other Water Conservation Calculators

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An online drip calculator that calculates the amount of waste from your leaky faucets. A service by the American Water Works Association.

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A tank performance calculator provided by the Domestic Roofwater Harvesting Programme at the School of Engineering, University of Warwick, England.

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