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Recreation Australia

Pool Volume Calculator Australia

Chemical doses, pump sizes and fill times all depend on how much water is in the pool. Choose the pool shape, enter its size and the shallow and deep end depths, and the calculator gives the volume in litres and kilolitres, how long it takes to fill and how much one centimetre of water adds.

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Same as shallow if the floor is flat.

Time a bucket of known size under the hose to measure it.

Pool volume

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In kilolitres

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Surface area

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Litres per centimetre of depth

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Time to fill

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Average depth

The working

    An estimate for planning. The volume is an estimate that assumes a straight slope. Always follow the label and your pool shop's advice when adding chemicals, and measure the water with a test kit.

    How do I calculate the volume of a swimming pool?

    For a rectangular pool, multiply length by width by average depth, then by 1,000 for litres. A 8 m by 4 m pool sloping from 1.0 m to 1.8 m has an average depth of 1.4 m, so the volume is 44,800 litres (44.8 kL). At 20 litres a minute it takes about 37 hours to fill.

    Measuring your pool

    Measure the water surface rather than the outside of the pool, and measure depth to the water level with a weighted tape or pole at the shallow and deep ends. For an irregular shape, split it into rectangles and circles, work out each and add them together.

    Kidney and freeform pools can be estimated as an oval of the same overall length and width, then reduced a little for the curves.

    Why volume matters

    Chlorine, balancing chemicals and algae treatments are dosed per thousand litres, so a wrong volume means the wrong dose. Pump and filter turnover is also based on volume, with pumps commonly sized to turn over the whole body of water at least once a day.

    Fill time matters for water restrictions: check your local water authority's rules on filling and topping up.

    To work out the pump, filter and chemical dose, follow the manufacturer's instructions.

    How this is calculated

    The rule, step by step, so you can check any figure by hand.

    • rectangular volume = length ร— width ร— average depth ร— 1,000 litres
    • round volume = ฯ€ ร— (diameter รท 2)ยฒ ร— average depth ร— 1,000
    • oval volume = ฯ€ รท 4 ร— length ร— width ร— average depth ร— 1,000
    • average depth = (shallow + deep) รท 2
    • litres per centimetre = surface area (mยฒ) ร— 10
    • time to fill = volume รท filling rate

    The average-depth method is exact when the floor slopes in a straight line from the shallow to the deep end. A pool with a steep drop-off, a deep hopper or a sunken section holds more or less than the estimate, so measure each section separately and add them for a closer figure.

    One cubic metre is 1,000 litres, which is why volume in cubic metres multiplied by 1,000 gives litres. The water level is normally a little below the coping, so measure the depth to the water line, not to the edge.

    A worked example

    A rectangular pool 8 m by 4 m, 1.0 m at the shallow end and 1.8 m at the deep end.

    1. Average depth1.4 m
    2. Volume44,800 L
    3. Kilolitres44.8 kL
    4. Litres per cm320 L
    5. Time to fill at 20 L/min37.3 hours

    44,800 litres.

    Check the figure with a water meter reading when you next fill the pool.

    Topping up water

    One centimetre of water over the pool's surface area is the surface area in square metres times 10 litres. In a 32 mยฒ pool, that is 320 litres. Evaporation, splashing and backwashing can take many centimetres a week in summer, so a pool cover pays for itself in water.

    What it leaves out

    Steps, benches, spa spill-overs and balance tanks add or remove water and are not modelled. The estimate is for planning, not for filling to the exact litre.

    What this calculator does not do

    • Straight-sloping floor assumed
    • Simple shapes only
    • No steps or benches
    • An estimate for planning

    Common questions

    How many litres are in my pool?

    Length ร— width ร— average depth ร— 1,000 for a rectangular pool.

    How do I measure an irregular pool?

    Split it into simple shapes and add the volumes.

    How long will it take to fill?

    Divide the volume by the hose flow in litres per minute.

    How much water is one centimetre?

    Surface area in square metres times 10 litres.

    Why does volume matter for chemicals?

    Doses are based on the litres of water to be treated.

    Where these numbers come from

    Method last reviewed 2026-10-28 This calculator uses fixed rules rather than rates that change, and its method is re-checked against the sources above at least once a year. Out of date? Tell us and we will fix it.

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