What to measure
How to use the pool volume calculator
- Pick the pool shape: rectangle, round or oval.
- Enter the length and width (or the diameter of a round pool) at the water line.
- For a rectangle, enter the water depth at the shallow end and at the deep end. For a flat floor, enter the same depth twice. Round and oval pools take one average water depth.
For a kidney or free-form pool, split it into a rectangle and a circle or oval, run each, and add the results.
The formulas
- Rectangle: length × width × (shallow depth + deep depth) ÷ 2
- Round: π × (diameter ÷ 2)² × depth
- Oval: π ÷ 4 × length × width × depth
- Gallons = cubic feet × 7.4805; liters = gallons × 3.785
Worked example: 32 × 16 ft pool, 3.5 to 8 ft deep
- Average depth: (3.5 + 8) ÷ 2 = 5.75 ft
- 32 × 16 × 5.75 = 2,944 cu ft (83.4 m³)
- 2,944 × 7.4805 = 22,023 gallons (83,365 liters)
- Salt for 3,200 ppm in fresh water: 588 lb
Common pool sizes
| Pool | Water depth | Gallons |
|---|---|---|
| 15 ft round | 4 ft | 5,288 |
| 24 ft round | 4.5 ft | 15,228 |
| 15 × 30 ft oval | 4.5 ft | 11,897 |
| 16 × 32 ft rectangle | 3.5 to 8 ft | 22,023 |
| 20 × 40 ft rectangle | 3.5 to 8 ft | 34,410 |
Frequently asked questions
How do I calculate how many gallons are in my pool?
Multiply length × width × average depth, all in feet, to get cubic feet, then multiply by 7.4805 (gallons per cubic foot). A 32 × 16 ft pool that goes from 3.5 to 8 ft deep averages 5.75 ft, so it holds 2,944 cu ft, or about 22,023 gallons.
How many gallons are in a round pool?
Diameter × diameter × water depth × about 5.9. A 24 ft round pool with 4.5 ft of water holds about 15,228 gallons. The 5.9 comes from π ÷ 4 × 7.4805.
How do I measure the depth of an above-ground pool?
Measure the water, not the wall. The water line sits a few inches below the top rail, so a pool with 52 inch walls usually holds well under 52 inches of water.
How long does it take to fill a pool with a garden hose?
Time how long your hose takes to fill a 5 gallon bucket. If it takes 30 seconds, the hose gives 10 gallons a minute, and a 22,023 gallon pool takes about 2,202 minutes, or 37 hours.
How much does the water in a pool weigh?
About 8.34 lb per gallon, so a 22,023 gallon pool holds roughly 183,700 lb of water, about 92 tons.
How much salt does a new saltwater pool need?
About 588 lb to bring 22,023 gallons of fresh water to 3,200 ppm. The calculator shows this for your pool; use the pool salt calculator if the water already has salt in it.
Sources
Formulas and defaults last reviewed October 30, 2026. How we check our math.