Pool Volume Calculator

Measure at the deep end and you overdose everything.

Measure at the deep end and you overdose everything. Pool volume for rectangular, circular and oval pools, using the average of the shallow and deep ends.

Written and maintained by Mohit PatelLast checked August 4, 2026How we build these

Shape

Length or diameter

Width

Shallow end depth

Deep end depth

Set to 0 for a flat-bottomed pool

Pump flow rate

L/h

Heat the water by

°C

Water volume

80,000 L

21,134 US gal · 17,598 imp gal · average depth 1.6 m

Surface area50 m²

Average depth1.6 m

Volume80,000 L

Cubic metres80

US gallons21,134

Imperial gallons17,598

Full turnover time6.7 hours

Energy to raise it 5 °C465 kWh

Using the deep end alone would say100,000 L

Measuring at the deep end alone would give 100,000 L — 25% too high, and every chemical dose calculated from it would be over by the same margin. Average the two ends, and remember the water line sits below the coping so the depth to measure is to the surface rather than to the rim.

How the Pool Volume Calculator works

Pool volume for rectangular, circular and oval pools, using the average of the shallow and deep ends. Every chemical dose is per unit of actual water, which makes this the number everything else depends on.

Also known as: how many litres in my pool · swimming pool gallons calculator · pool water capacity calculator · work out pool volume for chemicals

Average depth, and the third that goes missing

Almost no pool has a flat floor. Measuring at the deep end and treating it as the depth throughout overstates the volume of a typical sloped pool by around a third, and every chemical dose calculated from it is over by the same margin.

Averaging the shallow and deep ends is the right approximation for a linear slope, which most pools approximate. For a pool with a distinct deep section rather than a continuous slope, breaking it into two volumes and adding them is more accurate.

The second measurement error is depth to the rim rather than to the water line. Pools are filled some distance below the coping, and the difference is a real slice of volume — one that gets included in every calculation made from the physical dimensions.

Why the volume is the number everything depends on

Every dose, every chemical adjustment and every filtration calculation is per unit of water. A volume figure 30% high means every dose is 30% high, which wastes money, pushes levels out of range, and makes each subsequent correction wrong in the same direction.

Turnover time — how long the pump takes to circulate the whole volume once — comes from the same figure. Most guidance targets one or two full turnovers a day, and getting the volume wrong misjudges the pump schedule as well as the chemistry.

For a genuinely freeform pool, filling through a water meter is more accurate than any estimate from dimensions. It is a one-off measurement that then makes every future calculation right, which is worth the inconvenience once.

Heat, evaporation and the case for a cover

Raising water by 1 °C takes about 1.16 watt-hours per litre, so an 80,000 litre pool needs around 93 kWh per degree. Heating a pool is therefore expensive in a way that is easy to underestimate from the temperature difference alone.

Almost all of that heat leaves through the surface, mostly through evaporation. Which is why a cover saves more energy than any other single measure. It addresses the dominant loss path rather than adding input to compensate for it.

Evaporation is also the reason a pool loses water without leaking. Several millimetres a day is normal in warm weather, which on a large surface is hundreds of litres. The bucket test — floating a marked bucket of pool water and comparing the two drops — separates evaporation from a genuine leak.

Where to go next

The Pool Volume question rarely arrives on its own. These are the ones that usually come with it:

Volume Converter — An imperial pint is 20% larger than a US one.
Ring Size Calculator — Finger measurement to US, UK, EU and Japanese sizes.
Shoe Size Conversion Calculator — US, UK, EU, Japan and centimetres, from one measurement.
Bra Size Calculator — Band and cup from two measurements, UK and US.

Frequently asked questions

How do I calculate pool volume?

Surface area times average depth. For a sloping pool, average the shallow and deep ends — using the deep end alone overstates volume by around a third in a typical pool.

Why does pool volume matter so much?

Because every chemical dose is per unit of water. A volume 30% too high means every dose is 30% too high, which wastes money and pushes levels out of range.

Should I measure to the rim or the water line?

The water line. Pools are filled below the coping, and measuring to the rim adds depth that does not exist.

What is turnover time?

How long the pump takes to circulate the whole volume once. Most guidance targets a full turnover in six to eight hours, or two turnovers a day.

How much energy does heating a pool take?

Raising water 1 °C takes about 1.16 Wh per litre, so an 80,000 litre pool needs around 93 kWh per degree. That is why covers matter more than heaters — most heat is lost from the surface overnight.

Does an irregular pool need a different method?

Break it into rectangles and part-circles, calculate each, and add them. For a genuinely freeform shape, filling through a meter is more accurate than any estimate.

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