How much rainwater and greywater can you harvest at your home? Just fill in the five input fields and the calculator will show your rainwater harvesting potential in the following chart. Input What is your roof area (in square feet)? * Your roof area can be simply calculated by multiplying the length x width of your house. OutputSupply 1" rainfall supply from roof is (gallons) Roof area (sf) x 1/12(ft) x 7.48 (gal/cubic foot) Basin area needed to store 1" rainfall supply from roof is (sqft) Assuming your basin is 8" deep | 1in roof supply / (.667 ft * 7.48 gal/cubic foot) Your Annual roof rainfall supply is (gallons) Roof area (sf) x 1(ft) x 7.48 (gal/cubic foot) x 0.9 (runoff coefficient) Leave this field blank
