How much does a dripping tap really waste?

It depends almost entirely on how fast it is dripping, which is why counting matters more than estimating. At 1 drip a minute it is 131 litres a year. At 10 a minute, 1,314. At one a second, 7,884. Those are the same tap fault at different severities, and they differ by a factor of sixty.

Where does the 0.25 ml drop volume come from?

From the only figure anyone has published that was measured on actual taps. The United States Geological Survey measured a number of kitchen and bathroom sink taps and found drops between 0.2 and 0.33 ml, and uses 0.25 for its own calculations. Bath taps come in larger, at about 0.5 ml.

Other sites say a drop is 0.05 ml. Who is right?

Both, for different things. The 0.05 ml figure is the pharmacopoeial standard drop, defined for a laboratory dropper with an orifice around three millimetres across. It is a medicine-dispensing standard and it was never a measurement of a tap. Drop volume scales with the width of the rim the drop forms on, and a tap outlet is several times wider than a dropper tip, so the two figures are both correct for their own orifice.

What about the figure of 5,500 litres a year?

It is published by WaterSafe with Waterwise, and their page states the number and nothing else: no drip rate, no drop volume, no method and no citation. It is reachable, at about 42 drips a minute on the measured tap drop volume, which is a fast and badly worn tap. So the words doing the work are "up to". We are reporting that no method is published with it, not that it is wrong.

Is a dripping tap worth fixing?

That is a judgement about cost and effort rather than something this site can answer. What it can do is give you the number, so the judgement is made against a figure rather than a feeling. A slow drip is a small annual cost; a fast one is not.

My tap runs rather than drips. What then?

Then this calculator is the wrong tool, because a stream cannot be counted and the arithmetic here depends on a count. Once drops merge into a flow the honest measurement is at the meter, which measures volume directly rather than inferring it.

Dripping tap water loss

A tap dripping 10 times a minute wastes about 3.6 litres a day, which is 1,314 litres a year. Count the drips over a full minute, put the count in below, and the rest is arithmetic on a drop volume of 0.25 ml that you can change if you disagree with it.

Last reviewed 14 August 2026

What this calculator tells you

It converts a count of drips per minute into a daily volume, an annual volume and an annual cost, for one tap or several.

A daily volume in litres per day
An annual volume in cubic metres per year
An annual cost at your own supplier rate
The drop volume it used, as a field you can change

The drop volume is exposed rather than hidden because it is the single assumption the whole answer rests on. Change it and every output moves proportionally, which is the most honest way to show how much of the result is measurement and how much is convention.

How to take the measurement

Count the drips for a full minute, with a timer, and do it more than once. That is the entire measurement, and the two mistakes that matter are both about shortcuts.

Count for a full sixty seconds rather than fifteen and multiplying by four. A drip is irregular, so a short count magnifies whatever the tap happened to do in that window.
Count more than once and use the middle figure. Two counts that disagree tell you the tap is variable, which is itself useful.
Count the hot and the cold separately if both drip. They are separate faults and they may be dripping at different rates.

If the drops are merging into a thin stream, stop counting. how to count drips reliably covers where the countable range ends and what to do past it.

Using the calculator

Count the drips

Tap the button once for each drip. The rate fills in as you go, and you can type it instead if you have already counted.

No taps counted yet

Drips per minute

Drips per minute must be a number.

How many taps are dripping

Drip volume

Published figures for one drip run from 0.05 to 0.5 ml, so the answer moves by a factor of 10 depending which you take. Change it and watch what happens.

Who supplies your water?

It is on your bill. The rate per cubic metre comes from this company's charges scheme.

Rate of loss

0.000 litres per hour

What your result means

The useful thing about a drip rate is how steeply the answer climbs with it, which is why counting is worth the minute it takes.

It is also worth knowing where a drip sits against a real leak, because the gap is larger than most people picture. Four drips a minute is 0.06 litres an hour. The top band of the meter test on this site is 60 litres an hour, which is exactly a thousand times more. So a dripping tap and a burst supply pipe are not two points on the same scale in any useful sense, and a tap that has been dripping for a year has wasted what that supply pipe would waste in about eight and a half hours.

Drips per minute	Litres per day	Litres per year
1	0.36	131
10	3.6	1,314
30	10.8	3,942
60, one a second	21.6	7,884

Drip rate against annual volume, at a drop volume of 0.25 ml

A slow drip is a genuinely small annual volume. A fast one is a substantial share of a household total. Both look identical from across the room, which is the argument for counting rather than judging.

How the calculation works

Four multiplications and a division, and only one of them involves anything arguable.

Drips per minute × 60 for drips per hour, then × 24 for drips per day
Drips per day × the drop volume in millilitres
Millilitres ÷ 1,000 for litres, then × 365 for the year
Litres per year ÷ 1,000 for cubic metres, then × your volumetric rate

The arguable one is the drop volume, and it is worth two sentences here rather than none.

Published figures for a single drop range from about 0.05 to 0.25 ml, and that range is not a disagreement between measurements of the same thing. The higher figure was measured on real taps and the lower one is a laboratory dispensing standard defined for a dropper, and drop volume scales with the width of the rim the drop forms on. why published drip volumes differ by a factor of five sets out the physics, both sources and the arithmetic.

This site defaults to the measured tap figure rather than the midpoint of that range, because averaging a measurement with an inapplicable convention produces a number that describes no physical object. The field is adjustable from 0.05 to 0.50 so you can reproduce whatever another site publishes and see for yourself where their number came from.

Assumptions and sources

Drip Calculator: how much water does a leaking faucet waste?

United States Geological Survey, Water Science School · primary source

Faucet drip volume, adopted: 0.25 ml
Faucet drip volume, measured range: 0.2 to 0.33 ml
Bath tap drip volume: 0.5 ml
Drips per US gallon: 15140 drips
Drips per litre: 4000 drips

Tate's law: the weight of a falling drop

Thomas Tate, Philosophical Magazine, 1864, with the later drop-weight literature · primary source

Drop weight: W = 2 * pi * r * gamma equation

Litres in a cubic metre

Exact by definition

SI definition. The litre is defined as one cubic decimetre, so one cubic metre is exactly 1,000 litres.

Millilitres in a litre

Exact by definition

SI prefix definition. Milli is a factor of one thousandth.

Hours in a day

Exact by definition

Definition of the day as 24 hours.

Minutes in an hour

Exact by definition

Definition of the hour as 60 minutes.

Days used for an annual figure

Editorial convention

Annual figures on this site are a daily rate multiplied by 365. Leap years are not modelled, so a leap year is understated by one day, which is 0.27 per cent.

Measured range for a tap drip

Measured figure

United States Geological Survey, Water Science School. The upper end of the measured range for kitchen and bathroom sink taps, the lower end being 0.2 ml.

The drop volume of 0.25 ml comes from the United States Geological Survey, which measured a sample of kitchen and bathroom sink taps and found the volume to be between 0.2 and 0.33 ml. Two caveats travel with it and both are stated because they are real: those were American taps, and no sample size was published. It remains the only figure anywhere that was measured on taps at all, which is why it is used despite both.

Everything else on this page is arithmetic. Sixty seconds in a minute, twenty four hours in a day, a thousand millilitres in a litre, three hundred and sixty five days in a year. None of those needs a source and none of them is in dispute.

What to do next

Three things, and the first one changes the answer more than any of the others.

Count again, at a different time of day. Mains pressure varies, and a tap that drips slowly in the afternoon can drip faster overnight.
Count every dripping tap in the property rather than the worst one. The calculator multiplies by the number of taps, and two slow drips are the same as one fast one.
Change the drop volume to see how much the answer depends on it. If your conclusion flips between 0.2 and 0.33 ml, the honest answer is that the measurement is not precise enough to support the conclusion.

If the tap is running rather than dripping, the count stops being meaningful and the meter is the better instrument. measure a continuous stream at the meter instead measures volume directly.

Common questions

How much does a dripping tap really waste?: It depends almost entirely on how fast it is dripping, which is why counting matters more than estimating. At 1 drip a minute it is 131 litres a year. At 10 a minute, 1,314. At one a second, 7,884. Those are the same tap fault at different severities, and they differ by a factor of sixty.
Where does the 0.25 ml drop volume come from?: From the only figure anyone has published that was measured on actual taps. The United States Geological Survey measured a number of kitchen and bathroom sink taps and found drops between 0.2 and 0.33 ml, and uses 0.25 for its own calculations. Bath taps come in larger, at about 0.5 ml.
Other sites say a drop is 0.05 ml. Who is right?: Both, for different things. The 0.05 ml figure is the pharmacopoeial standard drop, defined for a laboratory dropper with an orifice around three millimetres across. It is a medicine-dispensing standard and it was never a measurement of a tap. Drop volume scales with the width of the rim the drop forms on, and a tap outlet is several times wider than a dropper tip, so the two figures are both correct for their own orifice.
What about the figure of 5,500 litres a year?: It is published by WaterSafe with Waterwise, and their page states the number and nothing else: no drip rate, no drop volume, no method and no citation. It is reachable, at about 42 drips a minute on the measured tap drop volume, which is a fast and badly worn tap. So the words doing the work are "up to". We are reporting that no method is published with it, not that it is wrong.
Is a dripping tap worth fixing?: That is a judgement about cost and effort rather than something this site can answer. What it can do is give you the number, so the judgement is made against a figure rather than a feeling. A slow drip is a small annual cost; a fast one is not.
My tap runs rather than drips. What then?: Then this calculator is the wrong tool, because a stream cannot be counted and the arithmetic here depends on a count. Once drops merge into a flow the honest measurement is at the meter, which measures volume directly rather than inferring it.