What a cubic metre of water looks like
A cubic metre is a cube one metre on each side. It holds 1,000 litres, weighs about a tonne, and is roughly 7 days of one person's household water use in England.
Last reviewed 14 August 2026
The short answer
One cubic metre, four ways of picturing it. The first is the definition and the rest are there because a definition is not an image.
| As | Is |
|---|---|
| A shape | A cube one metre wide, one metre deep and one metre tall. |
| A volume | 1,000 litres, exactly, by definition. |
| A weight | About a tonne. Water is close to a kilogram a litre. |
| Imperial gallons | 219.969 of them. |
| Household use | Roughly 7 days for one person in England, at the published average. |
The last row is the only one with conditions attached, and they are worth reading before using it, because the comparison flatters the reader in three separate ways.
How this works in practice
The reason this page exists is that a cubic metre is the unit a water bill counts in, and almost nobody has any feel for it. A leak reported as 4.4 cubic metres a year means nothing until it means something.
| Rate of loss | Cubic metres a year | Which is |
|---|---|---|
| 0.5 L/hr | 4.4 | About a month of one person's use in England. |
| 5 L/hr | 43.8 | About ten and a half months of one person's use. |
| 60 L/hr | 525.6 | More than ten people use in a year. |
That is the point of the unit conversion. The rate of loss at the top of the small leak band, which sounds trivial, is one person's entire annual household water use going into the ground.
What changes the answer
The size of a cubic metre does not change. The comparison to household use does, and it does so in three specific directions, all of which flatter the reader.
- The published average EXCLUDES supply pipe leakage. A meter reading includes it. On a leak calculator that is the caveat that matters most, because the very thing you are measuring is the thing the comparison figure leaves out.
- The average is adjusted upward for meter under-registration. A bill is not. So the published figure is slightly higher than what a meter would have shown for the same use.
- The average blends metered and unmetered households, and unmetered households typically use more. Anyone reading a consumption figure off a bill is metered, and is being compared against a number that includes people who are not.
Those three are not reconciled with a correction factor anywhere on this site. Three documented directional biases that a reader can weigh are worth more than one invented number nobody can check.
The figure is also England only, so a Welsh, Scottish or Northern Irish reader is being compared against an England average. expected household use per person per day covers what the figure is and is not.
Assumptions and sources
Water resources 2024 to 2025: analysis of the water industry's annual water resources performance
Environment Agency · primary source
- Household per capita consumption: 136.5 l/person/day
- Household per capita consumption, prior year: 137 l/person/day
- Household per capita consumption, dry-year adjusted: 140.3 l/person/day
- National leakage: 2617 Ml/day
- National leakage as share of water put into supply: 19 %
PR24 common performance commitments: per capita consumption (PCC), version 2.1
Ofwat · primary-standard source
- PCC formula: (measured household consumption + unmeasured household consumption) / total household population l/person/day
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.
Litres in an imperial gallon
Exact by definition
UK legal definition. The imperial gallon is defined as exactly 4.54609 litres in United Kingdom weights and measures law.
Hours in a day
Exact by definition
Definition of the day as 24 hours.
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.
Where the first severity band ends
Editorial convention
A practical threshold set just above the 0.4 litres per hour starting flow quoted for a DN15 meter with the TVM register. It is not a meter accuracy tolerance. Against the STANDARD it sits about 31 times below Q1, the 15.6 litres per hour at which OIML R 49-1 first defines any permitted error. Against THIS MANUFACTURER it sits about 6 times below 3 litres per hour, the lowest flow at which Itron volunteers a typical accuracy that the standard does not require. Neither figure reaches down to 0.5, so nothing quantifies a reading here on either footing. Meters with other registers start higher, so this threshold sits above the most sensitive case rather than above every meter.
The cube, the thousand litres and the gallons figure are definitions or arithmetic on definitions. Nothing about them is measured and none of them will change.
The household use comparison uses the published England figure of 136.5 litres per person per day, from the Environment Agency's annual analysis of water industry performance. Its three definitional caveats are on this page rather than in a footnote, because on a leak calculator the first of them is directly relevant to what the reader is measuring.
The weight is an approximation given as one. Water density varies with temperature and nothing here calculates with the figure.
What to do next
Two things, and the second is the more useful habit.
- Convert your own annual loss into cubic metres and compare it against your bill. Your bill counts in the same unit, so the two numbers are directly comparable without any conversion at all.
- When a figure is quoted in cubic metres anywhere, convert it once into something physical before deciding whether it is large. A number in an unfamiliar unit is not information yet.
Common questions
- How big is that really?
- About the size of a large domestic washing machine, or a chest freezer. Which is a useful thing to picture standing in a room, because the number on a water bill is a count of those and almost nobody imagines them as objects.
- How long does one cubic metre last a household?
- For one person in England, roughly 7 days at the published average of 136.5 litres per person per day. For a household of four, closer to 2 days. That average carries real caveats and they are set out below.
- Does a cubic metre of water really weigh a tonne?
- Near enough, and only as an image. Water is densest near four degrees Celsius and slightly less dense warmer, so the figure moves by a fraction of a per cent across ordinary temperatures. It is not a conversion to calculate with, and nothing on this site does.
- What does a cubic metre cost?
- That depends entirely on your supplier, and no rate on this site has been verified yet, so no figure is shown. What can be said without a rate is that one cubic metre is the unit your bill counts in, so the cost of a leak is always the number of these it adds multiplied by whatever your own rate is.