Rainwater Harvesting Calculator
Estimate annual harvestable rainwater from roof area, rainfall and runoff coefficient.
About this calculator
The rainwater harvesting calculator multiplies roof catchment area by average annual rainfall and a runoff coefficient to estimate the total volume of water that could be harvested per year.
Worked example
1,500 sqft roof, 900mm annual rainfall, 0.85 runoff
Result: Annual harvest ≈ 1,06,650 litres
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