Water Usage Calculator

Daily, Monthly, and Annual Usage are all calculated purely from your fixture counts and durations — showers, toilet flushes, laundry loads, and dishwasher runs. Water Rate is applied afterward, only to convert that fixed usage figure into Monthly Cost and Annual Cost, so it changes what you pay without changing how much water the model says you use.

They assume relatively efficient, modern fixtures: a 2.0 gpm WaterSense-ceiling showerhead (per EPA's WaterSense Showerheads specification) and a 1.6 gallon-per-flush toilet, the federal maximum set by the Energy Policy Act of 1992 and in effect for residential toilets since 1994 (per EPA's WaterSense Residential Toilets page). If your home has an older high-flow showerhead (2.5 gpm or more) or a pre-1994 toilet using 3.5 gallons or more per flush, your real usage will run higher than this estimate.

It's a fixed allowance for water uses this calculator doesn't ask about individually — cooking, drinking, hand and face washing, and similar small daily draws — added the same regardless of your other inputs. It's a rough placeholder rather than a measured figure, since these uses are harder to estimate per-household than fixture-based activities like showers or laundry.

At the default inputs, showers combine a relatively high per-minute flow rate (2.0 gpm) with several minutes of duration multiple times a week, which adds up faster than single-event uses like toilet flushes (1.6 gallons each) or a dishwasher cycle (4 gallons). Households with longer showers or more of them will see that share grow even further.