Above Ground Pool Calculator
Calculate how many gallons your round above-ground pool holds from its diameter and wall height, for chemicals and fill cost.
How this calculator works
Since nearly all above-ground pools are round, this calculator treats yours as a cylinder: it 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
An 18 ft (216 in) diameter above-ground pool filled 4 ft deep:
- Radius: 216 ÷ 24 = 9 ft
- Cubic feet: π × 9² × 4 ≈ 1,017.8760 ft³
- Gallons: 1,017.8760 × 7.48 ≈ 7,613.71 gallons
- At $0.01/gallon for fill water, that’s $76.14.
Coverage reference
| Pool size | Gallons |
|---|---|
| 108 in dia x 2 ft | 951.71 gallons |
| 216 in dia x 4 ft | 7,613.71 gallons |
| 432 in dia x 8 ft | 60,909.70 gallons |
How to measure your above-ground pool
Measure the pool’s inside diameter in inches and use your intended fill depth in feet — typically a few inches below the top rail, not the wall’s full height. If your pool is one of the less-common oval or rectangular kits rather than round, this cylinder formula won’t apply directly; approximate it instead as a rectangle scaled down by about 11% to account for the rounded ends.
Frequently asked questions
How many gallons does an above-ground pool hold?
It depends on diameter and fill depth — an 18-foot (216-inch) round pool filled to 4 feet holds about 7,614 gallons. Enter your pool's diameter and depth and this calculator returns the exact figure for chemical dosing and pump sizing.
Why are almost all above-ground pools round rather than rectangular?
Round pools distribute water pressure evenly around the wall, which lets manufacturers use lighter-gauge steel, resin, or aluminum wall panels without the bracing an oval or rectangular shape needs to resist corner stress. That's why round kits dominate the budget and mid-range above-ground pool market, while oval and rectangular models cost more for the same footprint.
My pool is oval, not round — can I still use this calculator?
Not directly — this calculator's cylinder formula is for round pools specifically. For an oval pool, a workable approximation is to treat it as a rectangle using the oval's overall length and width, then multiply that rectangular result by about 0.89 to account for the rounded ends, since an oval holds noticeably less water than the rectangle that bounds it.
Should I measure the pool wall's height or my actual water level?
Use your actual fill depth, not the wall's full height — above-ground pools are typically filled to within a few inches of the top rail (often around the middle of the skimmer opening), not brim-full. If your wall is 52 inches tall but you fill to 48, enter 48 for an accurate gallon count.
What size pump and filter do I need based on this gallon count?
Most above-ground pool pump/filter combos are sized to turn over the full pool volume once every 8-12 hours, so a 7,600-gallon pool needs a pump rated for roughly 630-950 gallons per hour at minimum. Manufacturers list a maximum recommended pool size (in gallons) for each pump model — match your calculated gallons to that spec rather than guessing by pool diameter alone.
Estimates only. Verify quantities with your supplier before purchasing.