Rooftop Rainwater Harvesting Collection Volume & Cistern Sizing Calculator
Calculate annual harvestable rainwater volume in Liters / Gallons and optimal storage cistern tank sizing based on roof catchment area, annual precipitation, and roofing material runoff efficiency.
Calculator Inputs
Live Real-TimeTotal Annual Harvestable Rainwater
Recommended Storage Tank / Cistern Size
11,813 L
Annual Harvested Volume in Gallons
24,964 gal
Detailed Calculation Breakdown
Calculation Methodology
Annual Yield (Liters) = Catchment Footprint Area (m²) * Annual Rainfall (mm) * Roof Runoff Coefficient (0.85). Recommended Tank Capacity (L) = (Annual Yield / 12) * 1.5 months reserve.
Important Legal & Educational Disclaimer
The standard first-flush diversion and gutter splash loss account for a 10% to 15% reduction from theoretical rainfall volume.
This calculator is designed for educational and informational purposes only based on public statutory frameworks. The outputs do not constitute binding financial, tax, or legal advice. We assume no liability for decisions made based on these estimations. Always verify with the relevant official authorities or a certified professional advisor.
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