| Enter the Roof area (RA): | m2 |
| Amount of rainfall (AF): | mm |
| Rainfall harvest: | liters |
Rainfall harvest = (RA * AF * 0.9 )
Where 0.9 is Amount of total rainwater expected for harvesting, AF is Amount of Rainfall, RA is Roof Area.
For example, when the roof area is 10m2, AF is 10mm, then ranifall harvest is 90 liters.