Optimize your sustainable living with our free Rainwater Collection Calculator. Quickly determine how many gallons of rainwater you can collect from your roof or specified area, considering local rainfall and surface efficiency. Perfect for gardening, irrigation, and reducing water bills.
Formula:
Rainwater Collected (Gallons) = Catchment Area (ft²) × Rainfall (inches) × Runoff Coefficient × 0.623
Where:
- Catchment Area (ft²): The horizontal projection of the area collecting rainfall (e.g., your roof size in square feet).
- Rainfall (inches): The average annual or per-event rainfall in inches for your location.
- Runoff Coefficient: A factor representing the efficiency of the collection surface (e.g., 0.75 for flat roofs, 0.90 for metal roofs, 0.85 for tiled roofs).
- 0.623: A conversion constant to transform square feet of area and inches of rainfall into U.S. gallons.