Pool Gallon Calculator — How Many Gallons Is My Swimming Pool?

How Pool Volume Is Calculated

Pool volume is calculated by multiplying the surface area by the average water depth. For a rectangular pool with a sloped floor:

Average Depth = (Shallow End + Deep End) ÷ 2

Volume (ft³) = Length × Width × Average Depth

Gallons = Volume (ft³) × 7.48052

A typical 16×32 ft rectangular pool with a 3.5–6 ft depth range holds approximately 24,000 gallons. Round and oval pools use a pi-based area formula; kidney pools use an approximation of 82% of the bounding rectangle.

Why Pool Volume Matters

• Chemical dosing: Every chemical dose (chlorine, pH adjusters, algaecides) is calculated per 10,000 gallons of pool water
• Pump sizing: Pool pumps must turn over the full volume every 6–8 hours — a 24,000-gallon pool needs a pump rated at 3,000–4,000 GPH
• Fill time: A standard garden hose flows ~9 GPM; filling 20,000 gallons takes about 37 hours
• Heater sizing: Pool heater BTU requirements are based on volume and temperature rise
• Salt systems: Salt cell chlorinators are sized by pool volume in gallons

Typical Pool Sizes & Volumes

• Small residential (12×24 ft, 3.5–5 ft): ~12,000–14,000 gallons
• Medium residential (16×32 ft, 3.5–6 ft): ~22,000–25,000 gallons
• Large residential (20×40 ft, 3.5–8 ft): ~35,000–40,000 gallons
• Lap pool (9×45 ft, 4 ft uniform): ~12,000 gallons
• Round pool (24 ft dia, 4 ft deep): ~13,600 gallons

Frequently Asked Questions