Pool Volume Calculator
Gallons = length × width × average depth (ft) × 7.48. A 32 × 16 ft pool from 3 1/2 to 7 1/2 ft deep (5.5 ft average) holds 21,065 gallons (79,740 L).
Pool volume
21,065 gallons
79,740 liters · US gallons
- Average depth used
- 5.5 ft
- Cubic feet
- 2,816 ft³
- Cubic meters
- 79.74 m³
Measure the water depth, not the wall height: water usually sits a few inches below the top.
How it works
Average depth = (shallow end + deep end) ÷ 2
Rectangle: ft³ = length × width × average depth
Round: ft³ = π × (diameter ÷ 2)² × average depth
Oval: ft³ = π ÷ 4 × length × width × average depth
Gallons = ft³ × 7.48052 (1 gal = 231 in³)
Assumptions
- The bottom slopes evenly between the shallow and deep ends. Pools with a sharp hopper or a long flat deep section hold slightly different volumes.
- Ovals are treated as true ellipses (Leslie's formula 3.14 × L × W × 0.25). Pools with straight sides and round ends hold a bit more.
- The calculator uses the exact 7.48052 gallons per cubic foot; the 7.5 shortcut in Leslie's formulas gives results about 0.3 % higher.
Worked examples
A 32 × 16 ft in-ground pool, 3 1/2 to 7 1/2 ft deep
- Average depth: (3.5 + 7.5) ÷ 2 = 5.5 ft
- 32 × 16 × 5.5 = 2,816 ft³
- 2,816 × 7.48052 = 21,065 gallons
Result: 21,065 gallons (79,740 L). The City of Akron table, using the 7.5 shortcut, lists 21,100 gal for a 16 × 32 ft pool at 5.5 ft average depth.
Checked by the automated test “pool — 32 × 16 ft rectangle at 5.5 ft = 21,065 gal”.
A 24 ft round above-ground pool with 4 ft of water
- π × 12² × 4 = 1,809.6 ft³
- 1,809.6 × 7.48052 = 13,536 gallons
Result: 13,536 gallons. Akron's table for a 24 ft round pool with a 52 in wall, using its 5.9 shortcut, says about 13,594.
Checked by the automated test “pool — 24 ft round at 4 ft = 13,536 gal”.
Measuring the water
- Measure the water, not the pool. Take length and width inside the walls, and depth to the water line. Above-ground pools are filled below the top of the wall, so the wall height overstates the water depth.
- Write the number on the equipment pad. Every dose and filter choice uses it, so measure once and keep it.
Common mistakes
- Using the deep-end depth for the whole pool. On a 3½ to 7½ ft pool that adds 36 % to the volume. Use the average depth.
- Treating a guess as fact. Leslie’s warns that overestimating the volume wastes chemicals and underestimating leaves the water unsanitary.
- Entering the radius instead of the diameter for a round pool. The box asks for the full width across.
Frequently asked questions
How do I figure out how many gallons my pool holds?
Measure the length and width of the water, then the depth at the shallow and deep ends. Multiply length × width × average depth to get cubic feet, then × 7.48 for gallons. Leslie's uses the same method with 7.5.
How do I calculate the volume of an oval pool?
Choose Oval. The calculator uses π ÷ 4 × length × width × depth, the same as Leslie's 3.14 × L × W × 0.25. A 15 × 30 ft oval with 4 ft of water holds 10,575 gallons; Leslie's table gives 10,600 for a 15 × 30 oval with a 48 in wall.
What about a kidney-shaped or free-form pool?
This calculator has no kidney shape. Leslie's gives (A + B) × length × 0.45 × average depth × 7.5, where A and B are the two widest points. You can also split the pool into a rectangle and circles and add them.
How many liters is my pool?
Switch the calculator to metric, or multiply gallons by 3.785 (1 US gallon = 3.785411784 L under NIST). The 32 × 16 ft pool above holds 79,740 L.
Sources
Formula, examples and sources checked on by the Yardstick Math team. How we check our formulas.
- How To Calculate Pool Volume — Leslie's
- How to calculate the gallons in a swimming pool — City of Akron, Ohio
- Handbook 44, Appendix C – General Tables of Units of Measurement (1 gal = 231 in³) — NIST