Water Usage Calculator
Estimate your daily and monthly household water usage based on common activities and appliances.
Formulas Used
Showers (gal/day) = Showers/day × Duration (min) × 2.1 gpm
Baths (gal/day) = (Baths/week ÷ 7) × 36 gal/bath
Toilet (gal/day) = Flushes/day × Gallons/flush
Dishwasher (gal/day) = (Loads/week ÷ 7) × Gallons/load
Hand Dish Washing (gal/day) = (Sessions/week ÷ 7) × 8 gal/session
Laundry (gal/day) = (Loads/week ÷ 7) × Gallons/load
Faucet (gal/day) = People × Minutes/person/day × Flow rate (gpm)
Outdoor (gal/day) = (Minutes/week ÷ 7) × Flow rate (gpm)
Total Daily = Sum of all categories
Monthly = Total Daily × 30.44
Annual = Total Daily × 365
Cost = Total gallons × $0.004/gallon
Assumptions & References
- Standard showerhead flow rate: 2.1 gallons per minute (gpm) — EPA WaterSense average.
- Average bath: 36 gallons — U.S. EPA estimate.
- Hand dish-washing session: 8 gallons (approx. 4 min at 2 gpm running water).
- Standard toilet: 6 gal/flush; Low-flow: 3.5 gal/flush; HE: 1.28 gal/flush — EPA WaterSense.
- Standard dishwasher: 6 gal/load; Energy Star: 3 gal/load — ENERGY STAR program data.
- Top-load washer: 40 gal/load (standard), 25 gal/load (efficient); Front-load HE: 15 gal/load — ENERGY STAR / AWWA.
- US average water usage: ~80–100 gallons/person/day (EPA, USGS).
- Average US water cost: $0.004 per gallon (~$3.38/Ccf) — AWWA 2023 Water Rate Survey.
- Month defined as 30.44 days (365 ÷ 12).
- Outdoor irrigation flow: user-supplied; typical garden hose ≈ 2 gpm, sprinkler system ≈ 1–3 gpm.
- Sources: EPA WaterSense, AWWA, USGS Water Science School.