Rainwater Harvesting Calculator

The general rule is that for every square meter of roof and every millimeter of rain, you can collect approximately 1 liter of water. However, there are losses from evaporation and filtration adjusted with the "runoff coefficient".

It is a percentage that indicates how much water is lost depending on the roof material. A metal or tile roof is very efficient (0.85-0.95), while a gravel or soil roof is much less efficient (0.1-0.3).

You should calculate the maximum expected rain volume in a month and cross-reference it with your estimated monthly consumption. A tank that is too small will overflow in storms, and one that is too large will be unnecessarily expensive.

Not directly. Water carries dust, bird droppings, and airborne particles. For human consumption, it must pass through sediment filters, activated carbon, and disinfection using UV light or chlorine.