Rainwater Collection Calculator

IMPORTANT UPDATE: As of July 1, 2023, several changes to the Rainwater Harvesting Rebate Program will take effect. Click here to learn more.

Calculator to Turn Raindrops into Gallons

To use this tool, calculate your roof’s area in square feet. Multiply roof length in feet by its width in feet. Enter that number in the blank field.  Example: 50 ft. X 30 ft. = 1500 square feet. Hint: If you don’t know your roof’s square footage, substitute your home’s square footage here. Then, enter the total annual rainfall in your area. For Tucson it is 12.17". The calculator does the rest giving you a ballpark estimate of gallons of rainfall you can potentially harvest in a year.

Tucson Rainwater Collection Calculation Estimator

Enter Your Roof Area (ft2)

Enter the Total Annual Rainfall for Your Area (in)

Tucson yearly average 12.17 inch
Total Annual Rainfall Potential (gal)

And remember, Tucson Water is ready to help you realize the benefits of harvesting rain with information, rebates, grant and loan programs for eligible families and individuals, plus access to free classes.