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CalcMax

Pool Volume Calculator

Range: 0 m – 1,000 m

Range: 0 m – 1,000 m

Range: 0 m – 10 m

Result

48,000 L

Volume in litres

Volume (US gallons)
12,680 gal (US)
Weight of the water
48.00 t

A pool volume calculator takes the length, the width and the depth of a rectangular pool and returns how much water it takes to fill it, in litres and in US gallons, along with the weight of that water. It is the same arithmetic as any rectangular volume — length times width times depth — with two differences that matter. The first is the unit: pools are quoted in metres, and a cubic metre is a thousand litres, so the multiplication arrives at litres directly and the gallons are a single division away. The second is what the answer is for. Nobody filling a pool wants to know its volume in cubic centimetres; they want to know how many litres the tanker or the hose has to deliver, and whether the deck underneath can take the weight when it is full, which is why this page prints the weight of the water as a third figure rather than leaving it as an exercise. That weight is worth looking at once: a cubic metre of water is a tonne, so a pool of 48 cubic metres holds 48000 litres and 48 tonnes of water, and the small garden pool in the first row of the table weighs more than a large car. The multiplication is exact and the page rounds to whole litres, which is the honest width for a figure whose inputs were measured with a tape: a 25-metre pool is rarely exactly 25 metres, and the depth is usually an average of a sloping floor rather than a single flat measurement. The one judgement call on this page is what depth to enter. Almost every real pool has a shallow end and a deep end, and this page takes a single depth box because a rectangular box is what it computes. Filling it with an average depth is the right move and the answer is exact rather than approximate: when the floor slopes in a straight line from one end to the other, the volume of water is exactly the same as a flat-bottomed pool at the average depth. A pool that steps — a shelf, a plunge section, a built-in bench — is a shape this page cannot see, and the average will be wrong by however much the steps hold. The table below reads the same way as the other volume pages: it starts at the size the page loads with, passes through a small garden pool and a half-length lap pool, and finishes at the 50-by-25 metre pool the Olympics are swum in, which is 2500000 litres and 2500 tonnes of water.

Rectangular pools from a paddling pool to a competition pool

Length (m)Width (m)Depth (m)Water (litres)Water (US gallons)Weight (tonnes)
841.5480001268048
320.424006342.4
63118000475518
220.832008453.2
105210000026417100
25102500000132086500
5025225000006604302500
000000

Eight pools in metres, and the first row is the one the page loads with. Three of them are worth finding by name: the 6 by 3 metre pool a metre deep is a plunge pool or a large spa at 18000 litres and 18 tonnes; the 25 by 10 metre pool at 2 metres deep is a short-course lap pool at 25 metres long, four lanes wide at 10 metres, 500000 litres and 500 tonnes; and the 50 by 25 row is the standard competition pool the Olympics are swum in, two and a half million litres weighing 2500 tonnes. Read the last two columns together on any row and the point of the page is visible: the litre figure is what you pay for, the tonne figure is what the ground has to carry, and they are the same number scaled by a thousand. The ratio between the two water columns is the check to run if a figure looks wrong — litres divided by gallons is 3.785 on every row, which is the number of litres in a US gallon, and a row where it is not is a row with a typo. The depth column is the average depth for a pool with a sloping floor, which is exact on a straight slope; the last row is all zeros, which is an empty pool and a legitimate answer rather than a blank. Every cell is recomputed from its row when the page is built, in metres, litres, US gallons and tonnes.

Formula

V(litres) = length × width × depth × 1000 V(gallons) = V(litres) ÷ 3.785411784 weight(tonnes) = length × width × depth

Length
The long side of the pool, in metres. The three length boxes all take metres by default because that is how pools are quoted and how a tape is read against one; centimetres, feet and inches are in the dropdown for anyone working from an old drawing or an imperial tape
Width
The short side, in metres. There is nothing special about which of the two horizontal measurements goes in which box beyond matching the shape, since the multiplication treats them alike — but a pool where the length and width are the same is a square pool, and the page will answer it correctly without comment
Depth
How deep the water is, in metres. For a pool with a sloping floor this is the average of the shallow end and the deep end, not the deep end: a 1 by 2 metre slope averages 1.5, and the volume computed from that average is exact because the two straight-line slopes on either side of it cancel. A pool with steps or a shelf has no such cancellation and this box cannot represent it
V(litres)
How much water the pool takes, in litres. A cubic metre is a thousand litres by definition, so this is the three lengths multiplied and then multiplied by a thousand — which is why the number is large and why nobody quotes it in cubic metres. It is printed to whole litres: rounding to four decimals would claim a precision a tape measure cannot deliver
V(gallons)
The same water counted in US gallons, which is what a pool is sold and dosed in on the other side of the Atlantic. One US gallon is exactly 3.785411784 litres, so this column is the litres divided by that constant. The ratio between the two columns is the same on every row of the table, which is the check that neither has drifted
weight
The weight of the water, in tonnes. A cubic metre of water is one tonne — a thousand litres at one kilogram each — so this figure is numerically the same as the volume in cubic metres, which the page does not otherwise print. It is the number for the structural question: what the filled pool puts on the ground or on a deck
1000
The number of litres in a cubic metre, by definition rather than by measurement: the litre was redefined in 1964 as exactly one cubic decimetre. It is the only conversion on the page that is exact, which is why the litres figure is as good as the three measurements it came from
3.785411784
The number of litres in one US gallon, exactly, being 231 cubic inches. It is worth knowing that this is the US gallon and not the imperial one: the imperial gallon is 4.54609 litres, about a fifth larger, and a page that quietly used the wrong one would be wrong by 20 per cent on every row

Use this page when you are filling a pool rather than measuring a solid. That means the answers you want are litres, gallons and tonnes — the units water is delivered in, dosed in and carried by — and the shape is the simple case: a rectangular pool with a floor that slopes evenly or not at all. The first thing to do with it is usually the biggest row of the table rather than your own numbers: find the pool closest to yours in size and read what filling it costs in water and what it weighs. A 6-by-3 metre pool a metre deep holds 18000 litres, which is 18 tonnes; a 25-metre lap pool 10 metres wide and 2 metres deep holds 500000 litres and weighs 500 tonnes, which is where a fill stops being a garden hose and becomes a tanker delivery. The weight column is the one people skip and later need. Water is unusually heavy for something you can swim in — a cubic metre is a tonne, and that is the same as a small car in a box the size of a fridge — so a pool of any size puts a load on whatever is under it that has to be designed for rather than discovered. If you are comparing this page with the aquarium page, the arithmetic is the same and the difference is the scale and the third column: an aquarium is quoted in litres and gallons and nobody weighs it, a pool is heavy enough that the weight is the reason the question gets asked. If you are comparing it with the cuboid page, that one answers in cubic centimetres with the surface area beside it, which is what you want if you are cutting panels rather than filling a tank. If your pool is round rather than rectangular, the calculation is a cylinder: the round pool pages are the cylinder volume calculator, where the radius and the depth go in instead. And if you are filling a pool whose floor steps down — a shelf along one side, a set of built-in steps — this page will be low by the volume those steps displace, because it can only see a box.

Worked examples

  1. An 8 by 4 metre pool, 1.5 metres deep

    1. Volume in cubic metres: 8 × 4 × 1.5 = 48
    2. Litres: 48 × 1000 = 48000
    3. US gallons: 48000 ÷ 3.785411784 = 12680.258…, which rounds to 12680
    4. Weight: 48 cubic metres at one tonne each = 48 tonnes

    The size the page loads with, and a good one to keep in mind as a yardstick: a modest garden pool holding 48000 litres, which is 48 tonnes of water. That is the same weight as a large lorry, spread over 32 square metres of ground. The gallons figure is worth a second look because of how it divides: 48000 litres is a round number of litres and a very unround number of gallons, 12680.26, which is what the table shows as 12680. The two columns are the same water; only one of them was designed to be round.

  2. A 6 by 3 metre pool, 1 metre deep

    1. Volume in cubic metres: 6 × 3 × 1 = 18
    2. Litres: 18 × 1000 = 18000
    3. US gallons: 18000 ÷ 3.785411784 = 4755.096…, which rounds to 4755
    4. Weight: 18 tonnes

    A small plunge pool or a large hot tub, and the row where the third column earns its place: 18 tonnes is a dozen family cars, standing on 18 square metres. That is the sort of figure that decides whether a pool goes on a deck or on the ground, and it is not visible from the litres column at all — 18000 reads like a quantity of water, 18 tonnes reads like a structural load, and they are the same number in different clothes.

  3. An Olympic pool, 50 by 25 metres, 2 metres deep

    1. Volume in cubic metres: 50 × 25 × 2 = 2500
    2. Litres: 2500 × 1000 = 2500000
    3. US gallons: 2500000 ÷ 3.785411784 = 660430.235…, which rounds to 660430
    4. Weight: 2500 tonnes

    The standard competition pool: 50 metres by 25, which is the size the Olympics are swum in, at the two metres of depth a competition pool is built to. Two and a half million litres, or 660430 US gallons, weighing 2500 tonnes. As a check on the columns, divide the litres by the gallons: 2500000 ÷ 660430 gives 3.785, which is the number of litres in a US gallon. That ratio holds on every row of the table and is the quickest way to tell whether a figure in either column has been mistyped.

  4. A pool with no water in it

    1. Volume: 0 × 0 × 0 = 0
    2. Litres: 0
    3. US gallons: 0
    4. Weight: 0

    Zero is a legal input rather than an empty box, and it is the one setting where the page's own answer is obviously right: no pool holds no water and weighs nothing. Leaving the boxes blank is the different case — with nothing entered the page shows no result at all, because there is nothing to work from. The distinction matters while typing, since clearing a box to retype a number should not flash up a row of zeros.

  5. A pool 3 metres by 2, 40 centimetres deep

    1. Volume in cubic metres: 3 × 2 × 0.4 = 2.4
    2. Litres: 2.4 × 1000 = 2400
    3. US gallons: 2400 ÷ 3.785411784 = 634.012…, which rounds to 634
    4. Weight: 2.4 cubic metres at one tonne each = 2.4 tonnes

    The smallest pool on the table, and the row that shows what the weight column's two decimals are for. At 2.4 tonnes the figure is 2400 kilograms — printing it to no decimals would round it to 2 tonnes and throw away 400 kilograms of water, which on a balcony or a roof is the difference between a paddling pool and a problem. The litres column is the one to use for filling it, the tonnes column for deciding whether it can go where you were planning to put it.

Limitations

The page computes a rectangular box, so the pool has to be rectangular: a round pool is a cylinder and belongs on the cylinder volume calculator, an oval one is an elliptical cylinder and this page will overestimate it, and a pool with a curved or free-form outline has no length and width to enter. The depth box takes one number, so a pool with a sloping floor needs the average of the shallow end and the deep end — which is exact when the floor slopes in a straight line, because the water lost at the shallow end and the water gained at the deep end cancel — but a pool with steps, a shelf or a plunge section has no such cancellation and the answer will be low by the volume those features displace. The outputs are in litres, US gallons and tonnes whatever the length boxes are set to, and the gallon is the US gallon: an imperial gallon is 4.54609 litres, about a fifth larger, so a reader in the UK working from the gallons column should divide the litres column by the imperial figure instead. Whole litres is a display width rather than a claim about precision: the three inputs were measured with a tape, a 25-metre pool is rarely exactly 25 metres long, and the depth is usually an average, so the last two or three digits of a large litre figure are not meaningful. The page does not subtract anything that is already in the pool — a pool part-filled, or one with a large volume of steps and fittings, is a case the box cannot see. It does not know about circulation, turnover, chemical dosing, evaporation or the volume of the filter and pipework, so it answers how much water the shell holds rather than how much water the system needs. It also does not know what water weighs in your units beyond the tonne it computes, and it does not account for salt or other dissolved solids, which raise the weight slightly above the fresh-water figure this page gives.

Frequently asked questions

How many litres of water does a swimming pool hold?
Multiply the length by the width by the depth in metres to get cubic metres, then multiply by a thousand: a cubic metre is a thousand litres by definition. An 8 by 4 metre pool 1.5 metres deep is 48 cubic metres, so 48000 litres. For a pool of that size the answer is best read alongside the weight, because 48 cubic metres of water is 48 tonnes, which is the figure that decides what the pool can stand on.
How do I convert the litres to gallons?
Divide by 3.785411784, which is the number of litres in a US gallon exactly. It is worth being sure which gallon you want: the US gallon is 231 cubic inches, while the imperial gallon used in the UK is 4.54609 litres, about a fifth larger. This page prints US gallons. The quickest check that neither column has been mistyped is to divide the litres by the gallons on any row — the answer is always about 3.785.
What depth do I enter for a pool with a sloping floor?
The average of the shallow end and the deep end. A pool that runs from 1 metre to 2 metres takes 1.5 metres. This is not an approximation: when the floor slopes in a straight line from one end to the other, the water missing at the shallow end is exactly the water gained at the deep end, and the volume equals a flat pool at the average depth. A pool that steps rather than slopes — a shelf along the side, built-in steps, a plunge pit — does not have that cancellation, and the average will be wrong by the volume of the steps.
How much does the water in a pool weigh?
One tonne per cubic metre, which is a thousand kilograms for a thousand litres. An 8 by 4 metre pool 1.5 metres deep holds 48000 litres and 48 tonnes of water; an Olympic pool at 50 by 25 metres and 2 metres deep holds 2500 tonnes. A cubic metre of water weighs the same as a small car, so a pool of any size is a structural load rather than a container of liquid, and that is why this page prints the weight rather than leaving it to be worked out.
Can I use this for a round pool?
Not accurately — a round pool is a cylinder, and the rectangular multiplication here will overestimate it. The cylinder volume calculator is the page for that shape: the radius and the depth go in, and its volume comes out in cubic centimetres, which converts to litres at a thousand to the cubic metre. An oval pool is an elliptical cylinder and needs the same treatment with two radii; a free-form pool has no length or width at all and cannot be answered by any of these pages.
Why does the page round to whole litres instead of giving decimals?
Because the inputs are measurements rather than definitions. A pool quoted at 8 metres is rarely 8.000 metres, the depth is usually an average of a sloping floor, and a tape read to the nearest centimetre already puts the third digit of a large litre figure in doubt. Whole litres is the honest width at this scale — 48000 rather than 48000.0000 — and it is the opposite of what the aquarium page does, where the volumes are small enough that the decimals carry real information.

References

Related calculators

Aquarium Volume CalculatorTank volume in litres and gallons from its dimensions.Cuboid Volume CalculatorVolume and surface area of a rectangular box.Cylinder Volume CalculatorVolume of a cylinder, plus the areas of its ends and its curved side.Pipe Volume CalculatorVolume and liquid capacity of a pipe or tube.