Garden planning
Rainwater Harvesting Calculator
Estimate water captured from one rainfall event, tank storage, overflow, and irrigation coverage.
Your estimate will appear here
Enter your project details and calculate for a practical planning estimate.
How this estimate works
- • One inch of rain on one square foot yields 0.623 gallons.
- • Captured water equals roof area × rainfall depth × 0.623 × collection efficiency.
- • Stored volume is capped at tank capacity; irrigation days equal stored gallons divided by daily demand.
Before you begin
- • This is not live rainfall data or a rainfall forecast; enter a measured or planned event depth.
- • It assumes an empty tank, a uniformly draining roof, and no ongoing withdrawals during the event.
- • Roof material, first-flush setup, debris, evaporation, freezing, local regulations, and water quality affect real-world results.
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