onlinecalculator.me

Free water usage and cost calculator

A water usage calculator breaks down daily and monthly water consumption by household activity. Enter your habits and local water rate to see where you use the most water and what.

About this calculator

How to use

  1. Enter the number of people in your household.
  2. Fill in your daily shower habits and bath frequency.
  3. Enter toilet flushes per day per person, dishwasher loads, and laundry loads per week.
  4. Add outdoor watering gallons per day if applicable.
  5. Set your water rate per gallon and click Calculate.

Formulas

showerGal/day = showersPerDay × showerMinutes × 2 gal/min
bathGal/day   = bathsPerWeek × 36 gal ÷ 7
toiletGal/day = flushesPerDayPerPerson × people × 1.6 gal
dishwasherGal/day = loadsPerWeek × 4 gal ÷ 7
laundryGal/day    = loadsPerWeek × 20 gal ÷ 7
totalDailyGal = sum of above + outdoorGal
monthlyGal    = totalDailyGal × 30.44
monthlyCost   = monthlyGal × pricePerGallon

Worked example

3-person household, default settings, $0.004/gal:

ActivityGal/day
Showers16.0
Baths15.4
Toilet28.8
Dishwasher2.9
Laundry11.4
Outdoor0.0
Total74.5

Monthly: 74.5 × 30.44 ≈ 2,267 gallons
Monthly cost: 2,267 × $0.004 ≈ $9.07

Notes

  • Rates are based on EPA WaterSense and ENERGY STAR standards for modern fixtures.
  • Older toilets (pre-1994) use 3.5–7 gallons per flush — significantly more than the 1.6-gallon low-flow standard.
  • Standard (non-HE) washing machines use 40+ gallons per load versus 15–25 for HE models.
  • Outdoor watering varies enormously — a single sprinkler zone runs 15–30 gallons per minute.

Frequently asked

How is water usage calculated?
Each activity is converted to gallons per day. Showers use 2 gallons per minute (EPA WaterSense standard). Baths average 36 gallons. Toilet flushes use 1.6 gallons (federal low-flow standard). Dishwashers use 4 gallons per cycle (ENERGY STAR). Laundry uses 20 gallons per load (HE washer). Monthly gallons equal daily gallons multiplied by 30.44.
What is the average water price per gallon?
The US average is roughly $0.004 per gallon ($4 per 1,000 gallons), though rates vary widely by city. Check your water bill for your exact rate — it is usually listed as dollars per hundred cubic feet (CCF) or per thousand gallons.
How do I find my water rate?
Look at your monthly water bill. Rates are often listed as price per CCF (hundred cubic feet) or per thousand gallons. 1 CCF = 748 gallons. Divide the dollar amount by the gallons to get price per gallon.
How can I reduce my water bill?
Shorter showers are the highest-impact change — cutting 2 minutes per shower saves about 4 gallons per shower. Installing a low-flow showerhead saves more. Running full dishwasher loads and fixing leaky faucets also make a significant difference.
How many gallons does the average American use per day?
The USGS estimates the average American uses 80–100 gallons of water per day indoors. Outdoor use adds significantly more in warm climates.
How do I share my water cost estimate?
Click Share to copy the page link, or Share with my numbers to include your household inputs in the URL.