Round pool size in square feet
A 15 ft round pool is 176.7 square feet of surface, an 18 ft is 254.5 and a 24 ft is 452.4. Halve the diameter to get the radius, square it, and multiply by pi. That surface figure sizes the cover and the chemical dose; the liner needs the wall area as well.
Round Pool Calculator
Standard round pool sizes
Above-ground round pools come in standard diameters: 12, 15, 18, 21, 24, 27, 30, and 33 ft. Each adds significant surface area: a 15-ft round = 177 sq ft; a 24-ft round = 452 sq ft; a 30-ft round = 707 sq ft.
For surface area: π × (diameter ÷ 2)². For a 24-ft round pool: 3.14159 × 12² = 3.14159 × 144 = 452.4 sq ft.
Liner area for round pools
Round pool liner = floor (π × radius²) + walls (π × diameter × wall height). For a 24-ft round, 4-ft wall pool: floor = 452 sq ft + walls (3.14 × 24 × 4) = 301 sq ft, total ~753 sq ft.
Replacement liners are sold by pool size (24-ft round × 52 in wall, etc.) - you don't order by square footage. But knowing the area helps for chemical dosing and water volume calculations.
Round pool surface area formulas
Round pools use the circle area formula: π × radius². The radius is half the diameter — measure across the widest point and divide by 2.
Common above-ground round pool sizes: 12 ft, 15 ft, 18 ft, 21 ft, 24 ft, 27 ft, 30 ft diameter.
12 ft diameter: π × 6² = 113 sq ft. 15 ft: 177 sq ft. 18 ft: 254 sq ft. 21 ft: 346 sq ft. 24 ft: 452 sq ft. 27 ft: 573 sq ft. 30 ft: 707 sq ft.
For semicircle pools or pool sections: use half the full circle area. Quarter circles (corner pools): use 1/4.
Pool deck area around a round pool: subtract the pool circle from the deck's outer circle (pool radius + deck width)². A 24 ft pool with 4 ft deck: outer circle = π × 16² = 804 sq ft. Minus pool: 804 - 452 = 352 sq ft of deck area.
Above-ground vs inground round pool sizing
Round pools come in two distinct types with very different installation requirements:
Above-ground round pools: typically 12-33 ft diameter, 48-54 inch wall height. Surface area ranges 113-855 sq ft. Material cost $1,500-7,500 for the pool kit. Installation $500-3,000 for site prep + assembly.
Inground round pools: less common, typically 12-25 ft diameter. Material + installation $20,000-60,000+. Often used for plunge pools or smaller backyard pools where space is tight.
Above-ground pool water volume: surface area × wall height × 7.5 × 0.9 (because water doesn't quite reach the top). A 24 ft above-ground pool with 52-inch walls: 452 × 4.33 × 7.5 × 0.9 = 13,206 gallons.
Inground round pools typically have deeper sections, so use average depth instead of fixed wall height.
Floor, wall and liner area for round pools
A round above-ground pool has three areas that people confuse, and buying the wrong one is expensive. The water surface is π × radius² and it governs covers, chemicals and heating. The wall is a rectangle wrapped into a cylinder: π × diameter × depth. The liner has to cover both, so it is the sum.
Most above-ground pools are 52 inches deep, which is 4.33 ft. That is the figure the table uses. A 48 in pool reduces the wall area by about 8%, and the deeper 54 in walls that come with some newer kits add about 4%.
Worked example — a 15 ft round pool with 52 in walls. Floor is 3.1416 × 7.5² = 176.7 sq ft. Wall is 3.1416 × 15 × 4.333 = 204.2 sq ft. A liner has to cover 380.9 sq ft in total, which is more than twice the surface area most people quote when asked how big their pool is.
Liners are sold by pool size, not by area, so you order a 15 ft round liner rather than 380 sq ft of vinyl. The area figure still matters: it is what tells you whether an overlap liner has enough material to fold over the top rail, and it is the basis for comparing a cheap 20-mil liner against a heavier 25-mil one by cost per square foot.
For covers, use the surface area but buy oversize. A solar cover is trimmed to the water surface, while a winter or safety cover needs a foot or more of overhang on every side to anchor, so its purchased size is a diameter or two larger than the pool itself.
| Diameter | Floor (surface) | Wall at 52 in | Total liner area |
|---|---|---|---|
| 12 ft | 113.1 sq ft | 163.4 sq ft | 276.5 sq ft |
| 15 ft | 176.7 sq ft | 204.2 sq ft | 380.9 sq ft |
| 18 ft | 254.5 sq ft | 245.0 sq ft | 499.5 sq ft |
| 21 ft | 346.4 sq ft | 285.9 sq ft | 632.2 sq ft |
| 24 ft | 452.4 sq ft | 326.7 sq ft | 779.1 sq ft |
| 27 ft | 572.6 sq ft | 367.6 sq ft | 940.1 sq ft |
Liners, covers, and round-pool-specific products
Round pools have their own product lines with size-specific pricing:
Round pool liners (above-ground): $150-500 depending on diameter and quality. 24 ft typical: $250-400. Premium beaded liners: $400-700.
Round pool covers: typically 2-3 ft larger diameter than the pool itself for cinching. Solar cover for 24 ft pool: $50-150. Safety cover: $400-1,000.
Round pool decks/surrounds: prefab kits available for 18-30 ft pools at $1,000-5,000 (deck only, not including the pool).
Filter and pump sizing: smaller than typical inground pools because water volume is less. A 24 ft above-ground pool (13,000 gallons) needs a 1 HP pump and 100-200 lb sand filter or 50-100 sq ft cartridge filter.
Pro tips
Diameter vs. radius
The radius is HALF the diameter. A “24-ft pool” has a 12-ft radius. Don't plug the diameter into the πr² formula by mistake.
Use 3.14159 for accuracy
Using 3.14 instead of 3.14159 is fine for most purposes. The difference on a 24-ft pool is less than 1 sq ft.
Add a fence-area calc
Pool code often requires fencing within X feet of the water. Calculate the fence area as a larger circle (pool radius + setback) - pool circle.
Cover allowance
Pool covers come oversized to overhang. A 24-ft round pool typically needs a 28-ft round cover for proper overlap.