Household Water Use Calculator
Estimate five selected direct household water uses; indirect and unmodeled uses are excluded.
Last updated · View algorithm, constants and default inputs (JSON)
About this calculator
Estimate five direct household uses from your inputs: shower flow, toilet flushes, running taps, dishwasher and laundry. The model assumes 4 US gal per dishwasher load and 15 US gal per laundry load. It excludes outdoor irrigation, leaks, bathing and indirect water used to make food or goods, so it is not a complete household or personal water footprint.
Worked example
calculated with the default values below
Minutes of showering per day 10 min · Showerhead flow 2 gpm · Toilet flushes per day 5 · Minutes of tap use per day 6 min · Dishwasher loads per week 4 · Laundry loads per week 4 Direct water use per day 50.5 gal · Direct water use per week 353 gal · Direct water use per year 18,417 gal · Largest modeled daily-use category Showers
General background references
Disclaimer
These calculators provide planning estimates only. Building codes, wiring regulations and safety requirements differ by country and change over time, and nothing here replaces a licensed professional or a permit. For structural, electrical or gas work, follow local code and have the installation inspected.
Implementation source
This record describes the implementation used by this page. It is not independent validation. External references, when available, support only the stated formula or definition; estimates and custom rules retain their own assumptions.
Formula and variables
G = m_s × q_s + n_f × 1.28 + m_t × 2.2 + n_d ÷ 7 × 4 + n_l ÷ 7 × 15
- m_s
- Shower minutes/day
- q_s
- Shower flow (gal/min)
- n_f
- Toilet flushes/day
- m_t
- Running-tap minutes/day
- n_d
- Dishwasher loads/week
- n_l
- Laundry loads/week
Direct-use model only: shower m×flow + flushes×1.28 + tap min×2.2 + dishwasher loads/week×4/7 + laundry loads/week×15/7. All volumes are US gallons; zero total means no largest category.
Frequently asked questions
What is included in the largest-use result?
It compares only the five modeled direct uses. Dishwasher and laundry use fixed assumptions of 4 and 15 US gallons per load; the other categories use the entered shower flow, flush count and tap time. A tie is resolved by the calculator’s list order. It is not a complete household water footprint, and all-zero inputs have no largest category.