Calculate My Pool
Units

Pool Volume Calculator

Pick the shape, enter the size and depth, and get the water in your pool in gallons and litres, with a drawing of the pool to check it.

Units
Pool shape
ft
ft
Depth profile
ft
ft

Water in your pool

19,150gallons

72,491 litres, 72.5 m³
US gallons
19,150gal
Litres
72,491L
Cubic metres
72.5m³
Cubic feet
2,560cu ft
Surface area
512sq ft
Average depth
5ft

Save this pool once and the chemical, salt and heater calculators start from it.

32 ft16 ftPlan area 512 sq ft
average depth 5 ft (dashed)3.5 ft6.5 ft32 ft
The math

  1. Surface area

    32 ft × 16 ft = 512 sq ft

  2. Average depth

    (3.5 + 6.5) ÷ 2 ft = 5 ft

  3. Volume of the pool

    512 sq ft × 5 ft = 2,560 cu ft

  4. US gallons

    2,560 cu ft × 7.4805 gal per cu ft = 19,150 gal

  5. Litres

    72.49 m³ × 1,000 L per m³ = 72,491 L

Gallons use 7.4805 per cubic foot; trade rules round it to 7.5, which adds 0.3 %.

A 32 by 16 foot rectangular pool whose floor slopes from 3.5 feet at the shallow end to 6.5 feet at the deep end holds 19,150 gallons, which is 72,491 litres or 72.5 cubic metres. Every pool volume is the same two numbers multiplied: the surface area of the water and its average depth. The shape decides how you find the area, the floor decides how you find the average depth, and this page does both, then draws the pool so you can see if the numbers look like your backyard.

How pool volume is calculated

Volume is surface area times average depth. Convert cubic feet to US gallons by multiplying by 7.4805. Trade rules round that to 7.5, which is 0.3 % higher and hardly matters for dosing.

Gallons = surface area (sq ft) × average depth (ft) × 7.4805

For the rectangle above: 32 × 16 = 512 sq ft, the average of 3.5 and 6.5 is 5 ft, so 512 × 5 = 2,560 cu ft, and 2,560 × 7.4805 = 19,150 gal. Litres are gallons times 3.7854, and cubic metres are litres divided by 1,000.

Measure the depth of the water, not the height of the wall. The waterline sits below the coping, and every inch you count that is not water adds 319 gallons to a 512 sq ft pool.

Pool volume by shape

Rectangle. Length times width. Round. π times the radius squared, so a 24 ft round pool at 4 ft deep is 452 sq ft, 1,810 cu ft and 13,536 gal. That matches the old shortcut of 5.9 × diameter² × depth used by pool suppliers.

Oval. π ÷ 4 times length times width, which is 78.5 % of the bounding rectangle. A 30 by 15 ft oval at 5 ft is 13,219 gal.

Kidney. The trade rule is 0.45 × (A + B) × length × average depth × 7.5, where A and B are the widths of the two lobes. The calculator uses the same factor as plan area equals 0.9 × the mean of the two lobe widths × length. With lobes of 12 and 18 ft, 25 ft long and 5 ft deep that is 337.5 sq ft and 12,623 gal.

L-shape. Add the two rectangles. A 30 by 12 ft main body plus an 8 by 10 ft leg is 440 sq ft; at 5 ft that is 16,457 gal.

Grecian and Roman ends. Enter the overall length, the width and how far each curved end bulges. The tool treats the straight middle as a rectangle and each end as a circular segment. At 32 ft overall, 16 ft wide and 3 ft bulges the plan is 482 sq ft instead of 512, and a 5 ft deep pool holds 18,019 gal.

Irregular shape or freeform. If you know the surface area from plans or a survey, enter it. Otherwise pick average length and width, or split the outline into rectangles and circles and add their areas. A freeform pool of 500 sq ft at 5 ft average holds 18,701 gal.

Depth profiles

A flat pool uses one depth. For a straight slope, add the shallow and deep depths and halve. A pool with a shallow flat, a slope, and a deep flat is weighted by length. Take a 32 by 16 ft pool that is 3 ft deep for the first 30 % of its length, 8 ft deep for the last 20 %, and slopes between: 0.3 × 3 + 0.2 × 8 + 0.5 × 5.5 = 5.25 ft average, so 20,108 gal. The same pool with one straight slope from 3 to 8 ft would be 21,065 gal, more than 900 gallons different, which is why the flats matter.

If your floor has a steep drop or a hopper, split the pool into sections with uniform slopes and add them.

Spa or hot tub attached

Turn on the spa option when it shares water with the pool. A 7 ft round spa with 3 ft of water adds 864 gal. A spa on its own circuit does not belong in the pool's volume.

What to do with the result

The result is saved as My pool on this device once you change an input, so the pool chemical calculator, pool salt calculator and pool heater calculator start with your gallons. Above-ground pools have their own size lists in the pool gallons calculator. To know how long a fill takes and what it costs, use the pool fill time calculator, and for water lost to the sun see the pool evaporation calculator. All pool tools are on the pool volume and water hub.

Metric pools

Switch the header toggle to metric and the defaults change to metres. A 10 by 5 m pool sloping from 1.1 m to 2 m holds 77.5 m³, which is 77,500 litres or 20,473 US gallons. Imperial gallons are 20 % larger than US gallons, so check which one a label uses.

Check the number

If you can, read your water meter during a fill and compare. Real pools have steps, benches and rounded corners, so expect a small gap. If the gap is large, remeasure the depth first: the average depth is the number people get wrong.