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Pool Volume Calculator
Quick answer: Multiply surface area by average depth, then by 7.48 to get US gallons. A rectangle's area is length times width; a round pool uses 3.1416 times the radius squared; an oval uses 3.1416 times half the length times half the width. Average depth is the shallow and deep ends added and halved.
How it works
Volume drives almost every other number on this site, from heat-up time to chemical doses. The calculator finds surface area from your shape, averages the shallow and deep readings, multiplies the two, and converts cubic feet to US gallons with the factor 7.48. It also shows litres (gallons × 3.785) for Canadian readers. Measure water depth, not wall height: most pools are filled a few inches below the coping. For a pool with a long flat shallow section and a short hopper, the simple average overstates volume a little, so take several depth readings and average those instead. Feed the result into the pool heater size calculator or the heating time calculator.
Worked example
Figures below are illustrative examples (2026-10-29), not quotes or guarantees.
Assumptions: rectangle 32 × 16 ft, 3.5 ft shallow, 6 ft deep. Area = 512 sq ft. Average depth = 4.75 ft. Volume = 512 × 4.75 × 7.48 ≈ 18,190 US gal (about 68,860 L).
FAQ
My pool is kidney-shaped. What do I enter?
Pick Oval and use the longest length and an average width; the result is a rough guide.
Why does chemical dosing need volume?
Product labels give doses per volume of water. Always follow the label, not a rule of thumb.
Does an above-ground pool work the same way?
Yes. Use the water depth, usually a few inches below the top rail. See above-ground pool heaters.
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