Water Demand Calculator
Estimate how much water a community needs each day, accounting for domestic use, commercial demand, and system losses.
What this calculator does
This tool estimates the total volume of water a community’s water system needs to supply each day, starting from residential per-capita use and scaling up to account for commercial and industrial demand as well as unavoidable system losses.
How it’s calculated
Domestic demand is population multiplied by average per-capita daily use (commonly 100-200 liters per person per day depending on climate, infrastructure, and lifestyle). A commercial and industrial add-on percentage scales this up to represent businesses, institutions, and light industry sharing the same supply network. Finally, the result is divided by (1 minus the non-revenue water percentage) to account for water that is produced but never billed — lost to leaks, theft, or metering inaccuracies — so utilities and planners know how much they actually need to produce, not just what customers consume.
These are planning-level estimates using commonly cited averages; actual demand varies with climate, season, water pricing, and local conservation practices, so utility-specific metered data should be used for engineering design.