Pool Volume Tables — Gallons, Litres and Surface Area by Pool Size

Aboveground pools

Figures below assume a 52-inch wall and a flat bottom, with an actual average water depth of about 44 inches. That distinction matters: a 52-inch pool is never filled to 52 inches. The nominal capacity printed on the box assumes a fill depth almost nobody uses, which is why box figures run high.

Aboveground pools — 52″ wall, approximately 44″ average water depth
Pool size	US gallons	Litres	Surface area (sq ft)
12 ft round	3,200	12,113	113
15 ft round	5,000	18,927	177
18 ft round	7,200	27,255	255
21 ft round	9,800	37,096	380
24 ft round	12,800	48,453	453
27 ft round	16,200	61,323	572
30 ft round	20,000	75,708	707
12 × 24 ft oval	6,400	24,226	240
15 × 24 ft oval	8,000	30,283	330
15 × 30 ft oval	10,000	37,854	410
18 × 33 ft oval	13,000	49,210	550

Inground pools

Figures below assume a typical rectangular vinyl-liner pool with two-foot radius corners, a 42-inch wall, a shallow-end fill depth of about 36 inches and a deep-end fill depth of about 90 inches, built to the common residential standard for pools of 16 × 32 feet and larger. Smaller pools in this table use a shallower deep end. The gallonage also allows for the water held in the plumbing and filter — roughly 100 linear feet of pipe plus filter capacity — which is a real volume that shorter tables leave out.

Inground rectangular vinyl-liner pools
Pool size	US gallons	Litres	Surface area (sq ft)
12 × 24 ft	8,900	33,690	288
14 × 28 ft	12,000	45,424	392
15 × 30 ft	13,800	52,239	450
16 × 32 ft	21,200	80,250	512
16 × 36 ft	23,900	90,471	576
18 × 36 ft	26,900	101,827	648
20 × 40 ft	33,000	124,918	800
20 × 44 ft	36,700	138,924	880

Calculating it yourself

For anything not in the tables, measure and multiply. All measurements in feet; the result is US gallons.

Rectangular pools: length × width × average depth × 7.5
Round, oval and free-form pools: average length × average width × average depth × 5.9
To convert to litres: gallons × 3.7854

The two multipliers differ because a rectangle fills its bounding box and a curve does not. Using 7.5 on a kidney-shaped pool will overstate its volume by a fifth or more, which is exactly the sort of error that produces a pool that never quite holds a chlorine residual.

Average depth is where people go wrong

Average depth is not the midpoint of the shallow and deep ends unless the floor slopes evenly the whole way, and in most pools it does not. A typical residential pool has a long flat shallow section, a short slope, and a deep hopper — so the true average sits closer to the shallow end than the arithmetic mean suggests.

For a pool with a flat shallow section and a hopper, a better approximation is to treat it as two volumes: the shallow area at its actual depth, plus the deep area at its average depth, added together. Measure the water depth, not the wall height, and measure from the water surface down.

Do not forget the plumbing

Pipes, the filter tank, the pump and the heater hold real water. On a small pool it is negligible; on a system with a large sand filter and a long run to a remote equipment pad it can be several hundred gallons. If precision matters — and it matters most when you are adding an expensive product or a strong oxidiser — add an allowance rather than ignoring it.

Why this number is worth getting right

Every dosing instruction on every container, every treatment described in this handbook, and every calculation of turnover on the pump run time page starts from volume. An owner who believes their 24-foot round pool holds 10,000 gallons when it holds 12,800 will chronically underdose by a quarter and will spend years wondering why their pool is harder work than everyone else's.

Because sanitisers and algicides are regulated pesticides, the dose on the label is the legally correct dose for the volume stated, and the EPA's guidance on reading a pesticide label is a useful primer on how those directions are structured. Getting the volume right is what makes following the label meaningful.