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Pool volume. Litres, cubic metres and gallons.

Work out how much water a pool holds. You need the volume for every chemical dose and for turnover calculations.

Pool volume calculator

Pool shape

Rectangle Round Oval Kidney or irregular L-shape

Units

Metric (m) Imperial (ft)

Depth

Constant Sloping

Oval type

True ellipse Straight sides, round ends

Length

Width

Average water depth

– litres

Enter all the measurements to see the volume.

The equation

V = L \times W \times \bar{D}

where

$V$: water volume (m³)
$L$: length (m)
$W$: width (m)
$\bar{D}$: average water depth (m)

Explain this equation

A rectangular pool is a box. Length times width gives the water surface area, and multiplying by the average depth gives the volume of water.

D-bar is the average water depth. On a flat-bottomed pool it is just the depth.

Measuring tips

Measure inside the pool shell at water level, not the coping. For a sloping floor, measure water depth at the shallow end and the deep end. A uniform slope averages correctly; a pool with a steep hopper or a deep-end well holds less than the straight average suggests, so split it into sections or take more depth readings and average them.

Fill-meter readings or the pool builder's drawings give a better figure than any shape formula. Use this as a working estimate.

Worked examples

Each example runs the calculator above with real measurements. Open one to see the equation, why it works and every step of the arithmetic.

Rectangular pool, 10 m × 5 m, 1.5 m deep

A rectangular pool 10 m long and 5 m wide with a flat floor and 1.5 m of water. The equation for this shape is shown with the calculator above.

Working

$V = 10.00 \times 5.000 \times 1.500 = 75.00 m³$
$75.00 m³ \times 1000 = 75,000 litres$
$\frac{75,000}{4.54609} = 16,498 UK gal$
$\frac{75,000}{3.78541} = 19,813 US gal$

Result

Water volume: 75,000 litres
75.00 cubic metres (m³)
75,000 litres
16,498 UK gallons
19,813 US gallons
Surface area 50.00 m². Volume rounded for display; use it as a working estimate.

Round pool, 4.5 m across, 1.2 m deep

A round above-ground pool 4.5 m in diameter holding 1.2 m of water.

V = \frac{π d^{2}}{4} \times \bar{D}

where

$V$: water volume (m³)
$d$: diameter (m)
$π$: pi, about 3.1416
$\bar{D}$: average water depth (m)

A round pool is a cylinder. The surface area of a circle is pi times the radius squared. Using the diameter (twice the radius) that becomes pi times d squared over 4, which saves halving your measurement first.

D-bar is the average water depth. On a flat-bottomed pool it is just the depth.

Conversions: 1 m³ = 1,000 litres. 1 UK (imperial) gallon = 4.54609 litres. 1 US gallon = 3.785411784 litres. 1 ft³ = 28.3168 litres.

Working

$A = \frac{π \times {4.500}^{2}}{4} = 15.90 m²$
$V = 15.90 \times 1.200 = 19.09 m³$
$19.09 m³ \times 1000 = 19,085 litres$
$\frac{19,085}{4.54609} = 4,198 UK gal$
$\frac{19,085}{3.78541} = 5,042 US gal$

Result

Water volume: 19,085 litres
19.09 cubic metres (m³)
19,085 litres
4,198 UK gallons
5,042 US gallons
Surface area 15.90 m². Volume rounded for display; use it as a working estimate.

Oval pool, 8 m × 4 m, 1.4 m deep

A true elliptical pool 8 m long and 4 m wide with an average depth of 1.4 m.

V = \frac{π}{4} \times L \times W \times \bar{D}

where

$V$: water volume (m³)
$L$: overall length (m)
$W$: overall width (m)
$π$: pi, about 3.1416
$\bar{D}$: average water depth (m)

A true ellipse has an area of pi times half the length times half the width. Written with the full length and width, that is pi over 4 (about 0.785) times L times W.

If your oval has straight sides with round ends, choose that option instead: it holds more water than a true ellipse of the same overall size.

D-bar is the average water depth. On a flat-bottomed pool it is just the depth.

Conversions: 1 m³ = 1,000 litres. 1 UK (imperial) gallon = 4.54609 litres. 1 US gallon = 3.785411784 litres. 1 ft³ = 28.3168 litres.

Working

$A = \frac{π}{4} \times 8.000 \times 4.000 = 25.13 m²$
$V = 25.13 \times 1.400 = 35.19 m³$
$35.19 m³ \times 1000 = 35,186 litres$
$\frac{35,186}{4.54609} = 7,740 UK gal$
$\frac{35,186}{3.78541} = 9,295 US gal$

Result

Water volume: 35,186 litres
35.19 cubic metres (m³)
35,186 litres
7,740 UK gallons
9,295 US gallons
Surface area 25.13 m². Volume rounded for display; use it as a working estimate.

Kidney pool, 9 m long, three widths

A kidney-shaped pool 9 m long, measured across at three evenly spaced points (3.2 m, 4.4 m and 3.6 m), with an average depth of 1.3 m.

V = L \times \bar{W} \times \bar{D}

\bar{W} = \frac{W_{1} + W_{2} + \dots + W_{n}}{n}

where

$V$: water volume (m³)
$L$: overall length (m)
$\bar{W}$: average width (m)
$W_{i}$: each measured width (m)
$n$: number of widths measured
$\bar{D}$: average water depth (m)

The average width method turns an irregular outline into an equivalent rectangle. Measure the width across the pool at several evenly spaced points along its length, including near each end, and average them.

The average width times the overall length gives the surface area. More widths give a better answer: three is a minimum for a kidney shape, five or more for a freeform pool.

A common shortcut for kidney pools, (A + B) × 0.45 × L, where A and B are the widths of the two lobes, gives a similar answer but measuring several widths is more reliable.

D-bar is the average water depth. On a flat-bottomed pool it is just the depth.

Conversions: 1 m³ = 1,000 litres. 1 UK (imperial) gallon = 4.54609 litres. 1 US gallon = 3.785411784 litres. 1 ft³ = 28.3168 litres.

Working

$\bar{W} = \frac{3.200 + 4.400 + 3.600}{3} = 3.733 m$
$V = 9.000 \times 3.733 \times 1.300 = 43.68 m³$
$43.68 m³ \times 1000 = 43,680 litres$
$\frac{43,680}{4.54609} = 9,608 UK gal$
$\frac{43,680}{3.78541} = 11,539 US gal$

Result

Water volume: 43,680 litres
43.68 cubic metres (m³)
43,680 litres
9,608 UK gallons
11,539 US gallons
Surface area 33.60 m². Volume rounded for display; use it as a working estimate.

L-shaped pool with a shallow leg

An L-shaped pool split into section A, 8 m × 4 m at 1.5 m deep, and a shallow section B, 3 m × 2.5 m at 0.9 m deep.

V = L_{A} \times W_{A} \times \bar{D_{A}} + L_{B} \times W_{B} \times \bar{D_{B}}

where

$V$: water volume (m³)
$L_{A}, W_{A}$: length and width of section A (m)
$L_{B}, W_{B}$: length and width of section B (m)
$\bar{D_{A}}, \bar{D_{B}}$: average depth of each section (m)

Split an L-shaped pool into two rectangles that do not overlap, work out the volume of each, then add them. Draw it out first and decide which piece the corner square belongs to, so it is only counted once.

Each section gets its own average depth, which suits L-shapes where the leg of the L is a shallow area or a sun shelf.

Conversions: 1 m³ = 1,000 litres. 1 UK (imperial) gallon = 4.54609 litres. 1 US gallon = 3.785411784 litres. 1 ft³ = 28.3168 litres.

Working

$V_{A} = 8.000 \times 4.000 \times 1.500 = 48.00 m³$
$V_{B} = 3.000 \times 2.500 \times 0.900 = 6.750 m³$
$V = 48.00 + 6.750 = 54.75 m³$
$54.75 m³ \times 1000 = 54,750 litres$
$\frac{54,750}{4.54609} = 12,043 UK gal$
$\frac{54,750}{3.78541} = 14,463 US gal$

Result

Water volume: 54,750 litres
54.75 cubic metres (m³)
54,750 litres
12,043 UK gallons
14,463 US gallons
Surface area 39.50 m². Volume rounded for display; use it as a working estimate.

Rectangular pool with a sloping floor

A 12 m × 6 m pool whose floor slopes evenly from 1.0 m at the shallow end to 2.0 m at the deep end.

V = L \times W \times \bar{D}

\bar{D} = \frac{D_{s} + D_{d}}{2}

where

$V$: water volume (m³)
$L$: length (m)
$W$: width (m)
$\bar{D}$: average water depth (m)
$D_{s}$: water depth at the shallow end (m)
$D_{d}$: water depth at the deep end (m)

A rectangular pool is a box. Length times width gives the water surface area, and multiplying by the average depth gives the volume of water.

With a sloping floor, the average depth is halfway between the shallow-end and deep-end depths. That holds for a straight, even slope. A pool with a steep drop or a hopper holds less than this, so split it into sections or average several depth readings.

Conversions: 1 m³ = 1,000 litres. 1 UK (imperial) gallon = 4.54609 litres. 1 US gallon = 3.785411784 litres. 1 ft³ = 28.3168 litres.

Working

$\bar{D} = \frac{1.000 + 2.000}{2} = 1.500 m$
$V = 12.00 \times 6.000 \times 1.500 = 108.0 m³$
$108.0 m³ \times 1000 = 108,000 litres$
$\frac{108,000}{4.54609} = 23,757 UK gal$
$\frac{108,000}{3.78541} = 28,531 US gal$

Result

Water volume: 108,000 litres
108.00 cubic metres (m³)
108,000 litres
23,757 UK gallons
28,531 US gallons
Surface area 72.00 m². Volume rounded for display; use it as a working estimate.

Related: dose the water with the pool chemical calculator, plan routine checks with the pool maintenance checklist, or size a balance or storage tank with the rectangular tank volume calculator and the cylindrical tank volume calculator. Convert units with the volume converter.

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More tools ›Calculators ›

Pool volume. Litres, cubic metres and gallons.

Pool volume calculator

The equation

Measuring tips

Worked examples

Rectangular pool, 10 m × 5 m, 1.5 m deep

Result

Round pool, 4.5 m across, 1.2 m deep

Result

Oval pool, 8 m × 4 m, 1.4 m deep

Result

Kidney pool, 9 m long, three widths

Result

L-shaped pool with a shallow leg

Result

Rectangular pool with a sloping floor

Result

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