Household Water Usage Calculator
Estimate your household’s daily and monthly water use — showers, toilets, laundry and dishes — and its cost.
How it works
daily = people × (showers × gal + flushes × gal) + (laundry loads × gal + dish loads × gal) ÷ 7 · monthly = daily × 30 · cost = monthly × $/gal
Indoor water use is the sum of the main fixtures. Showers and toilets scale with the number of people and their daily habits, so those are multiplied by the household size. Laundry and dishwasher use are weekly, so they’re divided by seven to fold into the daily total. Multiplying by 30 gives the monthly gallons, and your water rate turns that into a monthly cost.
Worked example
For 4 people: showers 4 × 1 × 17 = 68 gal, toilets 4 × 5 × 1.6 = 32 gal, laundry 5 × 20 ÷ 7 ≈ 14 gal, dishwasher 4 × 6 ÷ 7 ≈ 3 gal — about 118 gallons a day. That’s roughly 3,531 gallons a month, or about $21.19 at $0.006 a gallon.
Frequently asked questions
How much water does an average person use?
US indoor use averages around 60–80 gallons per person per day, and total use (with outdoor watering) often reaches 80–100 or more. Toilets, showers and faucets are the largest indoor shares, so efficient versions of those cut the biggest slices.
Why divide laundry and dishwasher by seven?
Those loads are entered per week, but the total is built as a daily figure so it can be scaled to a month cleanly. Dividing the weekly gallons by seven spreads them evenly across the days — five laundry loads a week becomes about 14 gallons a day.
What’s the fastest way to cut household water use?
Target the biggest shares first. Low-flow showerheads, dual-flush or 1.28-gallon toilets, and full loads only in the washer and dishwasher usually deliver the most. Outdoors, efficient irrigation and native plants often save even more than any single indoor change.
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This calculator is for educational purposes. Double-check important results before acting on them.