Pool Volume Calculator
How many gallons does your pool hold? Pick the shape, enter the dimensions and depths, and get gallons, liters, and cubic meters using the standard pool-industry formulas — the number every chemical dose and heater sizing chart starts from.
Gallons
21,120
L × W × avg depth × 7.5
Liters
79,948
Cubic meters
79.9
Avg depth
5.5 ft
These are the standard pool-industry multipliers: a cubic foot holds 7.48 gallons exactly — 7.5 rounds it for rectangles, and π/4 is baked into 5.9 for rounds (6.7 for ovals). Pools fill to mid-skimmer, a few inches below the top, so treat the result as a ceiling when dosing chemicals.
How Pool Volume Math Works
All three formulas are surface area times average depth times a gallons-per-cubic-foot multiplier. The pool industry's conventions are 7.5 for rectangles (a cubic foot holds exactly 7.48 gallons; 7.5 rounds it), 5.9 for rounds (π/4 folded into 7.48), and 6.7 for ovals. For a sloped pool, average depth is simply (shallow + deep) ÷ 2 — the default 32×16 ft pool with 3-ft and 8-ft ends averages 5.5 ft, so 32 × 16 × 5.5 × 7.5 = 21,120 gallons. A 24-ft round pool with a flat 4-ft depth works out to 24 × 24 × 4 × 5.9 = 13,594 gallons. The averaging assumes a constant slope; a hopper-style deep end holds a little less than the math says.
Industry formulas (gallons)
Rectangle: L × W × avg depth × 7.5 Round: D × D × avg depth × 5.9 Oval: long D × short D × avg depth × 6.7 Avg depth = (shallow + deep) ÷ 2 32×16 ft, 3' shallow / 8' deep: 32 × 16 × 5.5 × 7.5 = 21,120 gal 24-ft round, flat 4 ft: 24 × 24 × 4 × 5.9 = 13,594 gal 1 gal = 3.785 L · 1,000 L = 1 m³
Frequently Asked Questions
How many gallons is a 24-foot round pool?
With a flat 4-ft water depth, the industry formula gives 24 × 24 × 4 × 5.9 = 13,594 gallons. That lines up with the commonly quoted ~13,500 gallons for a 24-ft above-ground pool with 52-inch walls, since those actually hold about 4 feet of water once filled to the skimmer.
How do I calculate gallons for a pool with a shallow and a deep end?
Average the two depths and treat the pool as that deep throughout: a 32×16-ft pool sloping from 3 ft to 8 ft averages 5.5 ft, so 32 × 16 × 5.5 × 7.5 = 21,120 gallons. The average works exactly for a constant slope; if the deep end is a small hopper with a flat shallow section, true volume is somewhat less.
Why do pool formulas multiply by 7.5 instead of 7.48?
A cubic foot holds exactly 7.48052 US gallons, but the pool industry rounds to 7.5 for rectangles and bakes π/4 into the round-pool multiplier (7.48 × 0.785 ≈ 5.9). The rounding overstates volume by about 0.3% — roughly 55 gallons on a 21,000-gallon pool — which is negligible for chemical dosing.
How accurate are pool volume calculators?
Within about 5% for standard shapes. Real pools hold slightly less than the formula because water sits at mid-skimmer (several inches below the coping), walls have coving at the floor, and sloped 'average depth' math flatters hopper-bottom deep ends. When dosing chemicals, round the volume down rather than up.