RWH Calculator by Texas Cooperative Extension
A calculator for Texas that allows you to click on the city nearest you to calculate cumulative storage and supplemental water use for your rainwater harvesting system.
WaterWiser Drip Calculator
An online drip calculator that calculates the amount of waste from your leaky faucets. A service by the American Water Works Association.
Rainwater Tank Performance Calculator
A tank performance calculator provided by the Domestic Roofwater Harvesting Programmee at the School of Engineering, University of Warwick, England
Rainwater Harvesting Calculator
A rainwater harvesting calculator developed for a region in India. Inputs must be in metric units.
Water Conservation Calculator from Australia
A water conservation calculator developed by Melbourne Water in Australia. Warning: output is in metric units.