Pool Size Calculator

Pool Volume Formulas

• Rectangular: Length x Width x Avg Depth x 7.48 gal/ft^3
• Round pool volume calculator: pi x Radius^2 x Avg Depth x 7.48
• Oval: pi x (Length/2) x (Width/2) x Avg Depth x 7.48
• Kidney / freeform: Length x Width x Avg Depth x 7.0 (irregular bottom coefficient)

For sloped pools with a shallow and deep end, average depth equals (shallow + deep) / 2. This works for most residential pools where the floor slopes evenly.

Typical Pool Sizes

• Small round above-ground (12 ft x 48 in): about 3,400 gallons
• Medium round above-ground (18 ft x 52 in): about 8,600 gallons
• Small rectangular (16 x 32 ft, avg 5 ft): about 19,200 gallons
• Standard in-ground (20 x 40 ft, 3-8 ft slope): about 33,000 gallons
• Large in-ground (25 x 50 ft, 4-10 ft slope): about 65,400 gallons

Why Pool Size Matters

Gallons drive almost every other pool decision. Every chemical dose, from chlorine to cyanuric acid, scales directly with pool volume. Filter capacity, pump horsepower, heater BTU, and salt system size all depend on gallons. A small pool gallon calculator gives you a fast check before shopping for equipment or chemicals. Even a 10% error in volume means the same 10% error in chlorine, which matters for sanitation.

Above Ground vs In-Ground

An above ground pool volume calculator uses the same math as an in-ground calculator. Pick round for most Intex or soft-sided pools, oval for long above-grounds, rectangular for liner pools, and kidney for freeform gunite shapes. Above-ground pools usually have a consistent depth, so the single-average-depth option works fine. In-ground pools almost always have a sloped bottom, so use the shallow + deep option.