Round Pool Square Footage Calculator
Calculate round pool surface area using diameter or radius. Common above-ground sizes are 15, 18, 21, 24, 27, and 30 ft round.
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 12-30 ft diameter, 48-54 inch wall height. Surface area ranges 113-707 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.
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.