Garden & outdoors
Rainwater collection estimator
Translate rainfall and roof area into a potential collection volume.
A clear answer. Here’s how.
One millimetre over one square metre is one litre. Potential collection = catchment area × rainfall × supplied efficiency. Reports tank-limited collection and excess. Uses horizontal projected area and your assumptions, without forecasting rainfall or water quality.
See a worked example
Worked example
A fixed demonstration, separate from the values you enter above.
- Horizontal roof catchment area (m²)
- 60
- Rainfall (mm)
- 10
- Collection efficiency (%)
- 80
- Available tank space (litres)
- 500
Example result
- Potential collection
- 480 litres
- Tank-limited collection
- 480
- Excess volume (litres)
- 0