Round Pool Calculator
Calculate how many gallons your round above-ground pool holds from its diameter and wall height, for chemical dosing and fill cost.
How this calculator works
A round above-ground pool is a cylinder: this calculator converts your pool’s diameter (in inches) to a radius in feet, applies the cylinder-volume formula with your fill depth to get cubic feet, and converts to gallons at 7.48 gallons per cubic foot.
Formula: Radius (ft) = Diameter (in) ÷ 24. Cubic feet = π × Radius² × Height (ft). Gallons = Cubic feet × 7.48.
Worked example
A 15 ft (180 in) diameter above-ground pool filled 4 ft deep:
- Radius: 180 ÷ 24 = 7.5 ft
- Cubic feet: π × 7.5² × 4 ≈ 706.8583 ft³
- Gallons: 706.8583 × 7.48 ≈ 5,287.30 gallons
- At $0.01/gallon for fill water, that’s $52.87.
Coverage reference
| Pool size | Gallons |
|---|---|
| 90 in dia x 2 ft | 660.91 gallons |
| 180 in dia x 4 ft | 5,287.30 gallons |
| 360 in dia x 8 ft | 42,298.40 gallons |
How to measure your round pool
Measure the pool’s inside diameter in inches at the waterline, and use your actual fill depth in feet rather than the wall’s total height — most kits are filled a few inches below the top rail. Because volume grows with the square of the radius, double-check your diameter measurement carefully, since a small error there has a bigger effect on the gallon total than the same error in depth.
Frequently asked questions
How many gallons does a round above-ground pool hold?
It depends on diameter and water depth — a 15-foot (180-inch) diameter pool filled to 4 feet holds about 5,287 gallons. Enter your pool's diameter and depth and this calculator returns the exact figure, which you'll need for accurate chemical dosing.
Should I use the pool's wall height or the actual water depth?
Use your actual water level, not the pool wall's full height — most above-ground pools are filled a few inches below the top rail to leave freeboard for splashing and skimmer operation. If your wall is 52 inches but you fill to 48 inches, enter 48 for an accurate gallon count.
Why does the diameter matter so much more for round pools than rectangular ones?
Volume scales with the radius squared in the cylinder formula, so doubling a round pool's diameter roughly quadruples its volume for the same depth — a much steeper relationship than a rectangular pool's simple length-times-width scaling. Small measurement errors in diameter compound more than the same error would in a length or width measurement.
Is a 15-foot round pool a common size?
Yes — 15-foot, 18-foot, and 24-foot diameters are among the most common residential above-ground round pool sizes sold as kits, typically paired with 48-52 inch wall heights. Larger diameters hold dramatically more water, which affects everything from pump sizing to seasonal chemical costs.
Does the 'cost' shown here include chemicals or just water?
Just the fill water, using a default of $0.01/gallon that you should adjust to your local municipal or well water rate. Seasonal chemical costs, a pump/filter, and a winter cover are separate expenses this calculator doesn't estimate.
Estimates only. Verify quantities with your supplier before purchasing.