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Pool & Recreation

Pool Volume Calculator

Find how much water a pool holds, which is the number every chemical dose, heater sizing and pump calculation starts from. Pick the shape, enter the dimensions, and give the average depth rather than the deep end.

Pool dimensions

The fields change to match the shape you choose.

Shape
Rectangular pool
Depth
For a constant depth pool, enter the same figure twice. The calculator averages the two.

Your result

Sample values

21,082

US gallons

2,816

Cubic feet

79,801

Liters

17,556

Imperial gallons

Based on a 5.5 ft average depth.

What this volume means

Measure Figure
Turnover at 50 gpm7.0 hours
Salt for 3,200 ppm563 lb
Shock dose, 10 ppm17.6 lb
Water weight175,800 lb

How to use this calculator

  1. Choose the shape that most closely matches your pool. Kidney and freeform pools are usually closest to oval.
  2. Measure at the water line rather than the coping, and take the internal dimensions.
  3. Enter the shallow and deep end depths. The calculator averages them for a pool with a gradual slope.

Pools with a sudden drop

Averaging the two ends assumes the floor slopes evenly. If your pool has a flat shallow section and then a sharp hopper, split it: work out each section as its own rectangle and add the volumes. Averaging across a hopper overstates the volume, sometimes by a tenth or more.

Formula

Rectangular: Volume = Length × Width × Average depth

Round: Volume = π × Radius² × Average depth

Oval: Volume = π × (Long ÷ 2) × (Short ÷ 2) × Average depth

Gallons = Volume (ft³) × 7.48

Average depth
(Shallow + Deep) ÷ 2
7.48
US gallons in a cubic foot — use 6.23 for imperial

Multiply cubic feet by 28.317 for litres.

A 32 × 16 ft rectangular pool

Shallow end 3 ft, deep end 8 ft, with an evenly sloping floor.

  1. Average depth = (3 + 8) ÷ 2 = 5.5 ft
  2. Volume = 32 × 16 × 5.5 = 2,816 ft³
  3. US gallons = 2,816 × 7.48 = 21,082
  4. Litres = 2,816 × 28.317 = 79,801

About 21,000 US gallons — round down when dosing chemicals.

Understanding your results

Volume is the figure the rest of pool maintenance depends on. Chemical doses are quoted per 10,000 gallons, pump turnover is volume divided by flow rate, and heater sizing works from the mass of water being raised. An error here propagates into every one of them.

Round down when dosing

If you are using the number to add chemicals, take the conservative figure. Under-dosing is corrected by adding more an hour later. Over-dosing chlorine or salt means draining and refilling, which is slow and expensive. Most pools calculate slightly high because the walls curve in and the steps take up volume the shape formula ignores.

Steps, benches and tanning ledges

A set of corner steps typically removes 100 to 200 gallons, and a full tanning ledge considerably more. None of the shape formulas account for them, so if your pool has substantial built-in features, subtract a few percent from the result before using it for chemistry.

Questions

About this calculator

Ask something else

Oval gets closest for most freeform shapes. Measure the longest and widest points and accept that the result runs a few percent high, since the curves cut into the corners of the notional oval. For an irregular pool you care about precisely, split it into two overlapping shapes and add them.

Chemical dosing instructions sold in the US are in US gallons, and UK products are usually in litres. The two gallon figures differ by about 20 percent, which is enough to matter when shocking a pool, so check which unit your product assumes.

The water line. Most pools run four to six inches below the coping, and measuring to the top of the wall overstates volume by that much depth across the whole surface — several hundred gallons on an average pool.

Treat it as two calculations. Work out the flat shallow section at its own constant depth, then the hopper section using its own average, and add the two. A single average across the whole pool assumes an even slope and overstates the volume of a hopper pool.

No — it works from the internal dimensions you enter, which is what holds the water. Measure inside the liner rather than to the outside of the structure.

Keep going

All Pool & Recreation tools
Estimates, not specifications. Results are based on the values you enter and on typical material properties. Densities, coverage rates and product sizes vary between suppliers, so confirm quantities against your supplier's data before ordering. Structural work must be signed off by a qualified professional and meet your local building code.