Pool Volume Calculator (Round / Oval)

Round pool formula. Volume = π × radius² × average depth × 7.48. Radius is half the diameter. Most above-ground pools are round and most are flat-bottomed, so average depth equals actual depth.

Oval pool formula. Volume = π × (a × b) × average depth × 7.48, where a is half the long axis and b is half the short axis. An oval is essentially an ellipse.

The depth question for above-ground pools. Manufacturers list a wall height (e.g. 52 inches) but you almost never fill water all the way to the top. Subtract 6 inches for the actual water depth. A 52-inch wall holds about 46 inches of water = 3.83 feet.

Why pi shows up here and not in the rectangular calculator. The base shape of the pool (the footprint) determines which area formula you need. Rectangle = length × width, no pi. Circle = π × r². Ellipse = π × a × b. The depth multiplication is the same for all.

Worked example: a 24 ft round above-ground pool with 4 ft of water

• Radius = 12 ft
• Cubic feet = π × 12² × 4 = 1,810
• Gallons = 1,810 × 7.48 = 13,540

That puts it at the small end of “average backyard pool.” Most 24-footers actually hold 12,000 to 14,000 gallons depending on water height.

Sloped bottom on a round pool. Some inground round pools have a deep center. Use average depth: (shallow + deep) / 2. A round pool that goes from 3 ft at the wall to 6 ft in the center averages 4.5 ft.

The classic hand-calculation mistake. Working the formula out yourself, it is easy to put the diameter where it wants the radius, and because the radius is squared the answer comes out four times too large. A 24-foot pool that should hold 13,500 gallons reads 54,000.

This calculator asks for the diameter and halves it internally, so it cannot make that mistake on your behalf. But if you ever check the figure against something a pool store told you and the two are a factor of four apart, that is almost certainly what happened to whichever one is wrong.

The other one is depth. Above-ground pool owners routinely enter the wall height because that is the number printed on the box. Water sits several inches below the top rail, and a 52-inch wall usually holds about 46 inches. Entering 52 instead of 46 overstates the volume by 13%, which quietly under-doses every chemical you add for the life of the pool.