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Pool Volume Calculator

Find how much water your pool holds.

How it is calculated

Pool volume for a rectangular pool is V = length × width × average depth, with all three in metres, giving cubic metres. The tool then converts: litres = m³ × 1,000 and US gallons = litres / 3.785411784. For a pool that is shallow at one end and deep at the other, use the average of the two depths (roughly, depending on the slope). All values must be above zero. The shape is a plain box, so round, oval or kidney pools need a different formula, and the water level is normally a little below the rim, so the real fill is slightly less.

Worked example

A pool 8 m long, 4 m wide, average depth 1.5 m. Volume = 8 × 4 × 1.5 = 48.00 m³. Litres = 48 × 1,000 = 48,000 L. US gallons = 48,000 / 3.785411784 ≈ 12,680 gal. This is the amount of water to plan for chemicals and filling.

Try this example →

Common mistakes

  • Using the deepest point instead of the average depth, which overstates the volume.
  • Entering feet while the tool expects metres; the result would be far too small.
  • Applying it to a round or oval pool; a box formula overestimates the volume of curved shapes.
  • Mixing US gallons with imperial gallons; the gallon figure here is the US gallon (3.785 L).

About this calculator

This calculator estimates a rectangular swimming pool's water volume from its length, width and average depth (length × width × average depth), then converts the result into cubic metres, litres and US gallons. For pools with a shallow and deep end, enter the average of the two depths yourself to account for the sloped floor; round, oval or kidney-shaped pools need a different formula.

Pool owners calculating how much water is needed to fill up after maintenance, and anyone dosing chlorine or other chemicals (which are measured per litre or per gallon of water, not per square metre of surface) use this to get an accurate volume before buying supplies rather than guessing and over- or under-treating the water.

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Comments (1)

  • Editorial team

    Once you have the volume, divide it by your pump's flow rate to see how long a full turnover takes. A 48 m³ pool with a pump moving 8 m³ per hour needs about 6 hours to cycle all its water once. Chemical doses scale with volume, so a 10% error here becomes a 10% dosing error. What shape is your pool, and how did you estimate its average depth?

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