Water Usage Calculator

Please fill in the required fields with values greater than 0.
–gallons per day
–gallons per month
–gallons per year
–estimated monthly cost

Estimate only. Uses 20 gallons per laundry load and 6 gallons per dishwasher load. Your own habits and fixtures change the result.

How to use this calculator

Enter the number of people and your daily habits for showers, toilets, sinks, laundry and the dishwasher. Add outdoor watering if you want. Press Calculate to see your use per day, month and year.

The formula

Daily use = people × (shower minutes × flow + flushes × gallons per flush + sink use) + laundry and dishwasher use per day + outdoor use

Example: A family of 4 using 8 minute showers at 2.5 gpm, 5 flushes of 1.6 gallons and 8 gallons for sinks per person uses about 159 gallons a day, or about 4,766 gallons a month.

Understanding your household water usage

This calculator adds up the water your household uses for showers, toilets, sinks, laundry, dishes and outdoor watering. The daily, monthly and yearly totals help you see where your water goes and estimate what it costs.

A real-world example

Take a household of 3 people. Each takes an 8-minute shower with a 2.0 gallon-per-minute head (16 gallons), flushes a 1.28-gallon toilet 5 times (6.4 gallons) and uses 8 gallons at sinks. That is 30.4 gallons per person, or 91.2 gallons a day. Add 5 laundry loads a week at 20 gallons and 4 dishwasher loads at 6 gallons, and the total is about 109 gallons per day, or about 3,270 gallons in a 30-day month. If water costs $10 per 1,000 gallons, that is about $33 a month.

Main factors that change your usage

  • Shower length and flow rate: Showers are often the easiest place to save. Cutting 2 minutes from a 2.5 gpm shower saves 5 gallons each time.
  • Toilet age: Older toilets can use more than twice as much per flush as newer models.
  • Laundry: Older top-loading washers typically use more water per load than front-loaders.
  • Outdoor watering: Lawns and gardens can double summer use in some homes.

Tips and common mistakes

  • Time a few real showers instead of guessing.
  • Check the flow rate printed on your showerhead, or time how long it takes to fill a 1-gallon bucket.
  • Do not forget leaks. A running toilet can waste a large amount of water without being noticed.
  • Test for a toilet leak by adding a few drops of food coloring to the tank. If color shows up in the bowl without flushing, the flapper is leaking.

Checking your result against your bill

Compare the calculator’s monthly figure to your water bill. Many utilities bill in gallons, while others bill in CCF (100 cubic feet), which equals about 748 gallons. If your bill shows much more water than the calculator, you may have a leak. Turn off all fixtures and watch the meter. If it still moves, call a plumber.

Cost planning

Many utilities charge for sewer service based on water use, so your real cost per gallon may be higher than the water rate alone. Check your bill for both charges when entering a price.

Frequently asked questions

How much water does a household use?
The average US person uses about 80 to 100 gallons of water a day at home.
Which uses the most water in a home?
Toilets, showers, laundry and outdoor watering are usually the largest uses.
How much water does a shower use?
A standard showerhead uses 2.5 gallons per minute, so an 8 minute shower uses about 20 gallons. WaterSense heads use 2 gallons per minute or less.
How can I use less water?
Fix leaks, use low-flow fixtures, run full loads and water the garden early in the morning.
How much water do toilets use?
Modern toilets use 1.28 to 1.6 gallons per flush. Older ones can use 3.5 gallons or more.
How much water does a dishwasher use compared to hand washing?
Modern dishwashers typically use about 3 to 6 gallons per load. Washing the same amount of dishes by hand with the tap running can use much more. To save the most, run the dishwasher only when it is full and skip pre-rinsing, since most current models and detergents handle food residue well.
How much water does it take to water a lawn?
Lawns often need about 1 inch of water per week during the growing season, including rain. One inch over 1,000 sq ft is about 623 gallons. Water early in the morning to reduce evaporation, and water deeply but less often to encourage deep roots. Local watering rules may limit days or times.
How do I read my water meter?
Your meter is usually in a box near the street or in a basement. It shows a running total, often in gallons or cubic feet. Write down the reading, wait a set time, then read it again and subtract. Many meters also have a small leak indicator that spins when water is flowing anywhere in the house.