Rainwater harvesting
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Water per year48 m³
Worked example
Given: Roof area = 100 m²; Annual rainfall (mm) = 600; Runoff coefficient = 80 %
Result: Water per year = 48 m³
How it is calculated
1. Enter the values you know. 2. The calculator converts them to base units and applies the formula. 3. The result is shown in the unit you choose.
Frequently asked questions
How do I calculate it?
Given: Roof area = 100 m²; Annual rainfall (mm) = 600; Runoff coefficient = 80 %. Result: Water per year = 48 m³.
Is the calculator free and private?
Yes. It is free, needs no sign-up and runs in your browser — the numbers you type stay on your device.