FREE CONSERVATION TOOLS

Water calculators

Planning estimates. Actual use and collection depend on local conditions and system design.

Household water use

Number of residents: 4Daily litres per person: 135

Estimated household usage

540 L/day

16,200 litres per 30 days

Rainwater harvesting

Roof area: 120 m²Annual rainfall: 800 mmCollection efficiency: 80%

Estimated annual collection

76,800 L

Theoretical estimate adjusted by selected efficiency.

Formula: roof area (m²) × rainfall (mm) × collection efficiency. One mm over one square metre equals one litre. Choose rainfall from a reliable local source for a site estimate.