Running-Toilet Water-Waste Calculator: What Is It Costing You?

A running toilet can quietly waste hundreds to thousands of gallons of water a day. This free calculator uses cited EPA WaterSense and water-utility figures to show the honest range it is costing you each month and year — and the good news: it is almost always a $5-20 fix. Pick how bad the leak is, set your water price, and see the number.

How this calculator works

You do not need your water bill to get a useful answer, though it helps. Tell the calculator three things and it does the rest:

1. How bad the leak is. Pick “silent,” “audible / on-and-off,” or “constant” – or, if you have read your water meter, choose “Custom” and type your own gallons per day. Each preset maps to a researched range of gallons wasted per day, not a single guess.
2. Your water + sewer price. The box is pre-filled with the U.S. average, $15.33 per 1,000 gallons. Your real rate is printed on your water bill; type it in for a number that is true for your house.
3. How long it has been running (optional). Add the number of months and the tool also shows what the leak has likely cost you so far.

It then shows an honest monthly and yearly range – never one scary number – because the truth depends on how bad the leak actually is. The “Methodology and sources” panel inside the tool lists the per-severity gallon figures and where each one comes from.

The methodology (the real formula)

The math is deliberately simple and transparent, so you can check it against your own bill:

annual cost = gallons per day  x  365  x  (your price per 1,000 gallons / 1,000)

Monthly cost uses 30 days instead of 365. That is the entire model. There is no hidden fudge factor.

Two honesty rules are built in. First, results are shown as a range, low to high, because a “running toilet” covers everything from a seep you cannot hear to a valve that never shuts off. Second, gallon figures are rounded so the tool never fakes precision it does not have.

Here are the gallons-per-day bands the calculator uses, and where they come from:

• Silent leak – about 30 to 200 gallons/day. A slow seep you usually cannot hear; often only a dye test (a few drops of food coloring in the tank) reveals it. The EPA reports a leaky toilet can waste up to 200 gallons a day, and that roughly 10 percent of homes have leaks wasting 90 or more gallons a day.
• Audible / on-and-off run – about 200 to 4,000 gallons/day. You hear it refill on its own every so often. This is almost always a worn flapper that no longer seals; municipal utility figures put a worn-flapper run at roughly 1,000 to 4,000 gallons a day.
• Constant run – about 3,600 to 8,640 gallons/day. Water never stops. An open fill valve wastes roughly 3 to 5 gallons per minute (about 3,600 gallons a day), and a quarter-inch overflow stream can reach 7,200 to 8,640 gallons a day.

The default price, $15.33 per 1,000 gallons, is the U.S. average combined water and sewer rate (Bluefield Research’s 2024 U.S. Municipal Utility Water Rates Index, using 2023 data: roughly $7.23 water + $8.10 sewer per 1,000 gallons). Sewer is included on purpose: a running toilet’s water goes straight down the drain, so on most bills you pay for it twice – once to bring it in, once to take it away.

A worked example

Say your toilet has an audible, on-and-off run – the most common case – and you leave the price at the default $15.33 per 1,000 gallons. Take the middle of that band, about 1,000 gallons a day:

• Per day: 1,000 x 15.33 / 1,000 = about $15 a day
• Per month: 1,000 x 30 x 15.33 / 1,000 = about $460 a month
• Per year: 1,000 x 365 x 15.33 / 1,000 = about $5,595 a year
• Water wasted: 365,000 gallons a year

That is the typical point inside the audible band; the calculator shows the full honest range around it (roughly $92 to $1,840 a month) because your toilet might be at the low or high end. Now compare that to the fix: a flapper is about $5 to $15 and a fill valve about $10 to $20. Even at the bottom of the range, the part costs less than a single month of waste. That is the whole point of the tool – the leak is expensive and the fix is cheap.

When to use it – and when a new toilet pays off

Use this calculator the moment you notice a toilet that hisses, refills on its own, or never quite goes quiet. It turns a vague “I should get to that” into a real dollar figure, which is usually the push needed to fix it this weekend.

A few situations where the answer changes:

• Just fix the running part. For nearly every running toilet, the cure is a $5-$20 flapper or fill valve, not a new toilet. Replacing the toilet to stop a run is overkill.
• Consider a new toilet when the toilet itself is the cost. If your toilet predates 1994 it likely uses 3.5 to 7 gallons per flush (not per leak). A modern 1.28-gallon WaterSense model or 1.6-gallon standard toilet can pay for itself over a few years on flush volume alone in a busy household – separate from any leak. Run the numbers on flushes, not the running-leak presets, for that decision.
• Set your real rate first. Local water and sewer prices vary widely. If your bill is well above or below the $15.33 default, type in your real rate before you decide anything.

Honest caveats

This is an estimate, not a meter reading. Keep these limits in mind:

• Rates vary a lot. $15.33 is a national average. Some cities are half that; some are well more than double. Your bill is the only authority on your price.
• Leak severity is a range, not a fact. Two “audible” toilets can waste very different amounts. The presets are researched bands, not a measurement of your specific tank. If you want a real number, read your water meter with everything off, then again after some time, and use Custom mode.
• Flush volume is a different thing. This tool measures water wasted by a leak/run, not the water a healthy toilet uses per flush. Do not mix the two.
• The clock keeps running. A silent leak that you ignore for a year quietly adds up; the optional “months running” field shows roughly how much it has already cost.