basic

Rainwater Tank Harvest Volume Calculator

Gallons = roof area × rainfall × 0.623 × efficiency.

Estimates rainwater collected in gallons from roof footprint, rainfall depth in inches, and collection efficiency.

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Marcus Laurent By Marcus Laurent
Published Last reviewed 1 min read

Inputs

Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

Gallons = roof_ft² × rain_in × 0.623 × efficiency

In depth

Estimates rainwater collected in gallons from roof footprint, rainfall depth in inches, and collection efficiency.