SettingsSettings for this calculationUS
Check the tank lid or manufacturer stamp for the per-flush rating.
Toilets made before 1994 are commonly 3.5–7 gal (13–26 L) per flush; 1994–2014 models are commonly 1.6 gal (6 L).
WaterSense-certified toilets use 1.28 gal (≈4.85 L) or less per flush.
Some high-efficiency and dual-flush models use as little as 0.8–1.1 gal (3–4.2 L) on the low setting.
A commonly cited average is about 5 flushes per person per day.
Actual usage varies by household — adjust if you have a specific reason to expect more or fewer.
Number of people regularly using this toilet.
Count everyone in the household who uses this bathroom.
Your local water utility's volumetric rate, in the unit shown.
Check a recent water bill for your specific rate — it is billed per cubic meter (per kilolitre in some regions) or per 1,000 gallons in the US.
Water saved per year
12,200 gal
Figures that depend on a rate wait for yours — this page does not assume one.
They open the calculator with your figures already in it
Low-Flow Toilet Savings Calculator: 12,155 gal — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Annual volume saved = (old flush volume − new flush volume) × flushes per day per person × household size × 365; WaterSense-certified toilets use 1.28 gal (≈4.85 L) or less per flush, vs 1.6 gal (6 L) standard or 3.5+ gal (13+ L) pre-1994 fixtures
Inputs used
- Current Toilet (per flush)
- 3.5 gal
- New Toilet (per flush)
- 1.28 gal
- Flushes per Day per Person
- 5
- Household Size
- 3
- Water Rate
What this calculation does not cover
- Only the volumetric water rate you type in is applied. Sewer charges billed against metered water, fixed monthly service charges, and tiered block rates — where the marginal rate you actually save at is not the average rate on your bill — sit outside the arithmetic entirely.
- Nothing on the cost side of the swap is included: the toilet, the installation, disposal of the old fixture, or any utility rebate. This is a gross annual water saving, not a payback period or a return on the purchase.
- Flushing behaviour is assumed identical before and after — one flat volume per flush, the same flush count on both fixtures. Repeat flushes on a lower-volume bowl, a dual-flush full/reduced split, and leakage past a worn flapper or fill valve on either toilet are all outside the model.
- The per-flush figures are nameplate ratings you enter, not what the fixture delivers. A worn flapper, an adjusted fill line, a re-set flush valve or a displacement device in the tank all move the real volume, and the calculation cannot see any of it.
- Usage is 365 identical days at a fixed household size and a fixed rate. Vacancies, guests, seasonal occupancy, a household that changes size mid-year, and any rate rise or drought surcharge within the twelve months are not modelled.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-02 · in the site-wide review of 2026-09-06 · v1.1.1
Regulatory standards & verification citations1
- Annual volume saved = (old flush volume − new flush volume) × flushes per day per person × household size × 365; WaterSense-certified toilets use 1.28 gal (≈4.85 L) or less per flush, vs 1.6 gal (6 L) standard or 3.5+ gal (13+ L) pre-1994 fixtures
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