Drips per minute to litres per day
At the measured tap drop volume of 0.25 ml, one drip a minute is 0.36 litres a day and 131 litres a year. So multiply your count of drips per minute by 0.36 for litres a day, or by 131 for litres a year.
Last reviewed 14 August 2026
The short answer
Two multipliers do the whole job, and both come from the same arithmetic at the site default drop volume.
- Drips per minute × 0.36 gives litres per day
- Drips per minute × 131 gives litres per year
| Drips per minute | Litres per day | Litres per year | Cubic metres per year |
|---|---|---|---|
| 1 | 0.36 | 131 | 0.1 |
| 5 | 1.8 | 657 | 0.7 |
| 10 | 3.6 | 1,314 | 1.3 |
| 30 | 10.8 | 3,942 | 3.9 |
| 60, one a second | 21.6 | 7,884 | 7.9 |
That table is arithmetic, not estimation. Every row is the count multiplied by 60, by 24 and by the drop volume, then divided by 1,000 for litres and multiplied by 365 for the year.
How this works in practice
Four steps, and only the second one involves a number anybody could argue with.
- Drips per minute × 60 × 24 for drips per day, which is 1,440 per drip a minute
- Drips per day × the drop volume in millilitres
- Millilitres ÷ 1,000 for litres per day
- Litres per day × 365 for the year, then ÷ 1,000 for cubic metres
The drop volume is the whole of the uncertainty, so the most useful thing this page can do is show you how much of your answer it is responsible for.
| Drop volume | What it describes | Litres per year |
|---|---|---|
| 0.05 ml | The pharmacopoeial dropper convention. Not a tap. | 263 |
| 0.25 ml | Measured on kitchen and bathroom sink taps. | 1,314 |
| 0.50 ml | Measured on bath taps. | 2,628 |
A factor of ten between the top and bottom of that table, from one number. why published drip volumes differ by a factor of five explains why the first row is in the range at all and why this site defaults to the second.
What changes the answer
Three things, and they enter the arithmetic at different points.
- The drop volume, which multiplies the whole answer. It is the largest single source of uncertainty and it is an adjustable field for that reason.
- The count, which also multiplies the whole answer, and which is the part you control. A count taken over a full minute rather than fifteen seconds is the cheapest accuracy available here.
- The number of taps, which multiplies again. Two slow drips are one fast one as far as the volume is concerned.
What does not change the answer is the cost side, until you get there. The volume is the same in every supply area in the country, and only the money differs. your supplier rate per cubic metre is where that part comes from.
A leap year adds about 0.3 per cent to the annual figure. That is far smaller than the uncertainty in the drop volume, so it is not corrected for and it would be false precision to do so.
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
The pharmacopoeial metric drop, 20 drops to 1 millilitre
United States Pharmacopeia, British Pharmacopoeia and European Pharmacopoeia convention · primary-standard source
- Standard drop volume: 0.05 ml
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 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 conversion carries no assumption and needs no source: 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, a thousand litres in a cubic metre.
The one sourced figure is the drop volume of 0.25 ml, from the United States Geological Survey, which measured a sample of kitchen and bathroom sink taps. Two limitations travel with it wherever it appears on this site: American taps, and no published sample size. The page has been read directly, so the wording is the publisher's own, and its published conversions independently confirm the drop volume. That check is set out on the page about why drip figures disagree.
What to do next
Two things, and the second is the one that decides whether the first is worth acting on.
- Convert your own count. The two multipliers at the top of this page do it without a calculator if you want a rough figure first.
- Try the same count at 0.2 and at 0.33 millilitres, the two ends of the measured tap range. If your conclusion is the same at both, the answer is robust. If it flips, the honest position is that the measurement does not settle it.
And if the tap is running rather than dripping, none of this applies, because a count of a stream is not a measurement. measure a continuous stream at the meter instead measures the volume directly.
Common questions
- Where does 0.36 come from?
- 60 minutes multiplied by 24 hours gives 1,440 drips a day for a tap dripping once a minute. Multiply by 0.25 ml and divide by 1,000 and you have 0.36 litres. There is no assumption in the arithmetic, only in the drop volume.
- How much does the drop volume change the answer?
- Proportionally, and by a factor of five across the published range. The same 10 drips a minute is 720, 3,600 or 7,200 millilitres a day depending on whether you use the dropper convention, the measured tap figure, or a bath tap. That is why the field is adjustable rather than fixed.
- Which drop volume should I use?
- The measured tap figure, unless you have a reason not to. It is the only published figure that was measured on taps rather than on laboratory equipment, and it is the site default for that reason.
- Does this work for more than one tap?
- Yes, by multiplication. Two taps dripping at ten a minute produce the same volume as one at twenty, because the arithmetic only ever sees total drips. The calculator takes a number of taps so you do not have to do that step yourself.