> Rainwater harvesting Calculator

This rainwater harvesting calculator (operational since 2009 and commonly called a tankulator) works out what your expected rainfall collection capacity should be over a given year, along with your minimal tank size to have constant water given an average monthly demand.

Rainfall per Month


Looks for rows with columns named 'Month' (either 1 or Jan) and 'Monthly Precipitation' in millimeters, your average per month rainfall will be worked out for using the available data. For instance in Australia you can get that data here by selecting monthly rainfall and finding your nearest station and downloading the CSV file (top right).
Values for your roof
Water consumption

You should be able to work this out from your water bill by dividing by the months covered (usually 3)


Remember, the values calculated here should be taken as a working guide, it does not take into account other effects (such as drought conditions) and how complete the source data coverage is.

Reset & do another calculation.

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