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Rainwater Harvest Calculator
How much rainwater can I collect?
With our rainwater yield calculator, you can easily estimate how much rainwater you can collect from your roof or paved surface. Simply enter your location, area and roof type – we’ll calculate your potential annual or monthly harvest.

Learn more in the matching guide:

How much rainwater can I collect on my property?

Whether for watering, cleaning or cisterns – this guide helps you estimate how much rainwater you can collect from your roof or paved area.
Good to know: To maximize collection, use smooth surfaces like metal or flat roofs and clean your gutters regularly.

FAQ

How is the rainwater yield calculated?
The calculation is based on your roof area, the average annual rainfall at your location and the type of roof surface (runoff coefficient).
Why does roof type matter?
Depending on the material, more or less rainwater sticks to the surface and cannot be collected – especially with green roofs.
How accurate is the rainfall estimate?
We use average climate data. Local variations are possible – for precise planning, you can manually adjust the rainfall value.
What is a runoff coefficient?
The runoff coefficient describes the percentage of rainfall that actually reaches your collection system.
Can I use rainwater indoors?
Yes, but you need specialized filters and systems. For garden watering, simple collection setups are usually sufficient.

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