Water Usage Calculator

Most household water goes to a handful of uses — toilets, showers, laundry, faucets and, in summer, the garden. Enter how your household uses water and this calculator estimates the gallons (or litres) per day and month, what it costs, and how much you’d save with efficient fixtures.

Typical fixture flow rates

US federal standards cap showerheads at 2.5 gallons per minute and kitchen faucets at 2.2 gpm, and toilets sold today typically use 1.6 gallons per flush or less. EPA WaterSense-labelled products go further — for example showerheads of 2.0 gpm or less and toilets of 1.28 gpf or less.

How much water does a household use?

The US EPA’s WaterSense programme estimates that the average American uses about 82 gallons of water a day at home, and that more than half of household water use can go to outdoor watering in some regions during summer. Indoors, toilets, showers, faucets and clothes washers are the largest uses, with leaks adding a surprising amount in many homes. Your own use depends on household size, fixtures, climate and habits — the calculator lets you model yours.

Worked example

A household of three takes 8-minute showers with standard 2.5 gpm heads (60 gal/day), flushes 1.6-gallon toilets about 15 times a day (24 gal), uses bathroom and kitchen faucets (about 36 gal), runs the dishwasher five times and the washing machine five times a week (about 17 gal/day together), takes one bath a week and waters the garden for an hour a week. The calculator puts them at roughly 185 gallons a day. Switching to WaterSense showerheads and toilets, aerated faucets and a high-efficiency washer would save several hundred gallons a month.

Watering a lawn

One inch of water over one square foot is about 0.623 gallons. Many lawns need roughly an inch a week in summer, including rain; local extension services give better figures for your grass and climate.

Ways to use less water

• Fix leaks — a running toilet can waste hundreds of gallons a day.
• Install WaterSense showerheads, faucet aerators and toilets.
• Run the dishwasher and washing machine only with full loads.
• Water the garden early in the morning and only when needed.
• Use mulch and drought-tolerant plants.
• Check your water meter with no water running to spot hidden leaks.

Litres and gallons

Outside the US, water use is usually measured in litres and cubic metres. Switch the calculator to litres to see results in metric.

Where the water goes indoors

Toilets are often the single largest indoor use in homes with older fixtures, followed by showers, faucets and clothes washers. Leaks are a hidden category: a dripping faucet or a toilet flapper that doesn’t seal can waste more water than a person uses in a day. Because showers use both water and energy for heating, shorter showers and efficient showerheads save on two bills at once.

Reading your water bill

Water bills often charge separately for water supplied and sewer (wastewater), sometimes with tiered rates that rise with use, plus fixed monthly charges. Bills may be in gallons, thousands of gallons, cubic feet or CCF (hundred cubic feet); one CCF is about 748 gallons. Enter your combined water and sewer rate per 1,000 gallons to estimate costs.

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