Pool Volume Calculator

For a rectangular pool: multiply length × width × average depth to get cubic feet, then multiply by 7.48 (gallons per cubic foot). For example, a 15×30 ft pool with 5 ft average depth is 15 × 30 × 5 × 7.48 = 16,830 gallons. The calculator above handles rectangular, oval, round, L-shaped, kidney, and irregular shapes automatically.

Every pool chemical dose is expressed per 10,000 gallons. If your volume is wrong, every chemical dose is wrong. Too little wastes money and leaves the pool under-treated; too much can overshoot target levels and damage equipment or irritate swimmers. Accurate volume is the foundation of all pool chemistry calculations.

Approximate volumes for common pool sizes (at 5 ft average depth): 12×24 ft = ~10,800 gal; 15×30 ft = ~16,800 gal; 16×32 ft = ~19,200 gal; 18×36 ft = ~24,300 gal; 20×40 ft = ~29,900 gal. Round pools: 12 ft diameter = ~3,400 gal; 15 ft = ~5,300 gal; 18 ft = ~7,600 gal; 24 ft = ~13,600 gal (at 4 ft depth).

For a round above-ground pool: Volume (gallons) = π × radius² × depth × 7.48. Or use the simplified formula: diameter² × 5.9 × depth. For example, an 18 ft round pool filled to 4 ft: 18² × 5.9 × 4 = 7,646 gallons. Note that actual water depth is typically 6–12 inches less than the wall height.

For pools with a shallow end and deep end, average depth = (shallow end depth + deep end depth) ÷ 2. For example, a pool that is 3 ft at the shallow end and 8 ft at the deep end has an average depth of (3 + 8) ÷ 2 = 5.5 ft. Use this average depth in all volume calculations. If your pool has a gradual slope, this two-point average is accurate enough for chemical dosing purposes.