Pool Volume Calculator: Gallons and Litres for Any Pool
Pool Volume Calculator
Work out how many gallons or litres a swimming pool holds from its shape, size and depth, for rectangular, round, oval and kidney pools, in ground or above ground, with a sloped floor if it has a shallow and a deep end. The page also gives how long it takes to fill from a hose, what the water weighs, the pump flow for an eight hour turnover and the figure to use on chemical labels.
Hours to fill, by flow
The same pool in other shapes
Volume is surface area times average water depth, with 7.48052 US gallons to the cubic foot, 1,000 litres to the cubic metre and water at 8.34 lb a gallon. A sloped floor is averaged from the shallow and deep ends, which is exact for a straight slope and a little high for a pool with a steep hopper at the deep end. The kidney formula is the industry approximation, 0.45 times the sum of the two end widths times the length. Measure water depth, not wall height: an above ground pool is usually filled to 4 to 6 inches below the top of the wall. The CSV, image and printed report contain the values you entered, nothing preloaded.
How to use this tool
Choose the shape, give the length and width, or the diameter for a round pool, and pick feet or metres. Then give the water depth: the shallow end, and the deep end if the floor slopes. Leave the deep end empty for a level floor, which is what nearly every above ground pool has. The gallons and litres appear as you type, with fill time, water weight and pump size below.
The input people most often get wrong is depth. The page wants the depth of the water, not the height of the wall. An above ground pool with a 52 inch wall is filled to about 46 inches, halfway up the skimmer, and using the wall height instead makes the answer about 13 percent too high. Measure the inside diameter too, not the frame.
What the calculation is doing
Every pool volume is the area of the water surface times the average depth. A US gallon is defined as 231 cubic inches, and a cubic foot is 1,728 cubic inches, so each cubic foot holds 1,728 divided by 231, 7.48052 gallons. In metric it is simpler still: a cubic metre is 1,000 litres.
The shape only changes the area. A rectangle is length times width. A circle is pi over four times the diameter squared, which is where the rule of thumb of diameter squared times depth times 5.9 comes from, since 0.785 times 7.48 is 5.875. A straight sided oval is a rectangle with a half circle at each end, and a kidney is estimated with the industry formula of 0.45 times the sum of the two end widths times the length.
Above ground round pool gallons
| Round pool | 48 in wall, 42 in water | 52 in wall, 46 in water | 54 in wall, 48 in water |
|---|---|---|---|
| 12 ft | 2,961 | 3,243 | 3,384 |
| 15 ft | 4,627 | 5,067 | 5,288 |
| 18 ft | 6,662 | 7,297 | 7,614 |
| 21 ft | 9,068 | 9,932 | 10,364 |
| 24 ft | 11,844 | 12,972 | 13,536 |
| 27 ft | 14,991 | 16,418 | 17,132 |
| 28 ft | 16,122 | 17,657 | 18,425 |
| 30 ft | 18,507 | 20,269 | 21,151 |
| 33 ft | 22,393 | 24,526 | 25,592 |
US gallons, with the water 6 inches below the top of the wall. Each figure opens the calculator on that pool.
In ground pool gallons
| In ground pool | 4 ft level | 3.5 to 6 ft | 3.5 to 8 ft |
|---|---|---|---|
| 12 x 24 ft | 8,618 | 10,233 | 12,388 |
| 14 x 28 ft | 11,729 | 13,929 | 16,861 |
| 15 x 30 ft | 13,465 | 15,990 | 19,356 |
| 16 x 32 ft | 15,320 | 18,193 | 22,023 |
| 18 x 36 ft | 19,390 | 23,025 | 27,872 |
| 20 x 40 ft | 23,938 | 28,426 | 34,410 |
US gallons, straight sloped floor. A deep end with a steep hopper holds a little less.
Why the oval matters more than people think
Most online pool calculators treat an oval as a true ellipse. Most above ground oval pools are not: they have straight sides and round ends, held by buttresses. For a 15 by 30 foot pool the difference is 402 square feet of water against 353, so the ellipse formula comes out 12 percent low. On chemicals dosed by volume, that is enough to under treat the pool every time.
In ground pools with freeform shapes are harder. For those, split the surface into rectangles and half circles, or measure the water added during a fill with the meter, which is the most reliable number of all.
A worked check you can repeat on paper
Take the page’s starting pool: 16 by 32 feet, 3.5 feet at the shallow end and 6 feet at the deep end. The surface is 512 square feet. The average depth is halfway between 3.5 and 6, which is 4.75 feet, so the volume is 512 times 4.75, 2,432 cubic feet. Times 7.48052 gallons per cubic foot, that is 18,193 gallons, or 68,867 litres.
From a hose delivering 8 gallons a minute, 18,193 gallons takes 2,274 minutes, about 37.9 hours. The water weighs 8.34 pounds a gallon, 75.8 tons in all. A pump turning it over in 8 hours needs 18,193 divided by 480, about 38 gallons a minute.
What to do with the number
Chemicals. Pool chemical labels give doses per 10,000 gallons. Divide your gallons by 10,000 and multiply the label dose by the result; the page shows that multiplier. Getting the volume right is the whole point of the exercise, because an overestimate means over dosing and an underestimate means a pool that never quite clears.
Pump and filter. A common rule for home pools is to circulate the whole volume in about 8 hours. Public pools work to tighter turnover times set by local codes.
Top ups. The gallons per inch figure tells you how much water a week of evaporation or a backwash costs, and what a water bill should look like after a refill.
Mistakes that catch people out
Using the wall height. Water sits 4 to 6 inches below the top of an above ground wall.
Measuring the frame. Measure the inside of the liner, wall to wall. On a 24 foot pool, measuring 6 inches too wide adds about 4 percent.
Treating a straight sided oval as an ellipse. Pick the straight sided option for most above ground ovals.
Averaging a hopper deep end as a straight slope. A diving pool with a steep hopper holds less than the straight line average suggests. For those, split the pool into a shallow section and a deep section and add them.
Forgetting steps and benches. Built in steps take up a few hundred gallons. It rarely matters for chemicals, but it does for a precise fill.
Popular calculations
Each opens the calculator on that pool with its own address, and every value can be changed once it is open. Above ground pools are filled to 6 inches below the top of the wall.
Above ground round pools
Above ground oval pools, straight sides
In ground rectangular pools
Kidney pools
Metric
How this was checked
The engine was tested in Node against hand calculations and against the rules of thumb pool professionals use. The 16 by 32 foot pool gives 18,193 gallons exactly; the trade shortcut of 7.5 gallons per cubic foot gives 18,240, 0.26 percent high because it rounds 7.48052 up. A 24 foot round pool 4 feet deep gives 13,536 gallons against 13,594 from the 5.9 shortcut, 0.4 percent apart for the same reason. A 4 by 8 metre pool 1.5 metres deep gives exactly 48,000 litres.
Every address in the lists above was then opened and checked for a distinct title, the right answer, charts that render, and clean CSV, image and print output containing only that pool, at desktop, tablet and phone widths.
Common questions
How many gallons are in a 24 foot round above ground pool?
About 12,972 gallons with a 52 inch wall filled to 46 inches, 11,844 with a 48 inch wall and 13,536 with a 54 inch wall. The table on this page covers every common size from 12 to 33 feet.
How many gallons are in a 16 by 32 inground pool?
About 18,193 gallons with a floor sloping from 3.5 to 6 feet, and 22,023 if the deep end is 8 feet. At a level 4 feet it would be 15,320.
How do I calculate how many gallons my pool holds?
Work out the water surface area in square feet, multiply by the average water depth in feet, then multiply by 7.48, the number of US gallons in a cubic foot. For a round pool the area is 0.785 times the diameter squared; for a sloped floor use the depth halfway between the shallow and deep ends.
How long does it take to fill a pool with a garden hose?
At a typical 8 gallons a minute, about 10.6 hours for a 15 foot round above ground pool and 38 hours, over a day and a half, for a 16 by 32 inground pool. Time your hose filling a bucket to get your own flow and enter it on the page.
How many gallons of water is an inch in my pool?
Surface area times 0.623. For a 16 by 32 pool that is about 319 gallons per inch, which is useful for working out how much water was lost to evaporation or a backwash.
What size pump does my pool need?
A common rule for home pools is to turn the whole volume over in 8 hours, so divide the gallons by 480 for the flow in gallons a minute. A 18,193 gallon pool needs about 38 gallons a minute. Pipe size and filter rating also matter, so check with the equipment maker.
Related Calculators and Reference
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