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🌧️ Rainfall Collection Calculator

Calculate how much rainwater you can collect from your roof based on area and annual rainfall.

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About Rainfall Collection Calculator

Calculate how much rainwater you can collect from your roof based on area and annual rainfall. Free online tool, no registration needed.

Rainfall Collection Calculator in 3 steps

  1. Enter your roof area in square meters
  2. Enter your local annual rainfall in millimeters
  3. Click Calculate to see your collection estimate

Frequently Asked Questions

How much rainwater can I collect?

Multiply roof area (m²) by rainfall (mm) and divide by 1000 for cubic meters. We apply 85% efficiency.

Is data uploaded?

No. All calculations run locally in your browser.

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What is Rainfall Collection Calculator?

Rainfall Collection Calculator is a free online tool that runs entirely in your browser. No download or signup needed — enter Roof Area and Annual Rainfall to get results instantly. All data is processed locally.

Use Cases

Key Features