Choose your pool shape, enter its size and the depth at each end, and get the volume in US gallons and litres. The calculator also shows the surface area, the weight of the water and how long it takes to fill at your hose flow rate. Free and private, it runs in your browser.
Last updated: October 2026
Assumes a floor that slopes steadily from the shallow to the deep end. Enter equal depths for a flat floor.
A pool is a shape with a surface area and an average depth. Find the area from the outline, multiply by the average depth to get the volume, then convert to gallons or litres. Chemical doses, heaters and pumps are all sized from this number, so it is worth getting right.
A rectangular pool is 32 ft long and 16 ft wide. The shallow end is 3 ft deep and the deep end is 7 ft, so the average depth is (3 + 7) ÷ 2 = 5 ft. The volume is 32 × 16 × 5 = 2,560 ft³, and 2,560 × 7.48 ≈ 19,150 US gallons, or about 72,500 litres. Filling it from a hose that delivers 9 gallons per minute takes about 35 hours.
Volumes are approximate and use the average depth shown.
| Pool | Depth | Average depth | US gallons |
|---|---|---|---|
| 12 × 24 ft rectangle | 3 to 5 ft | avg 4 ft | 8,618 |
| 16 × 32 ft rectangle | 3 to 7 ft | avg 5 ft | 19,150 |
| 18 ft round | flat 4 ft | avg 4 ft | 7,614 |
| 24 ft round | flat 4.5 ft | avg 4.5 ft | 15,228 |
| 15 × 30 ft oval | 3.5 to 5.5 ft | avg 4.5 ft | 11,897 |
Water weighs about 8.35 pounds per US gallon, or 1 kilogram per litre. A 19,150-gallon pool therefore holds roughly 160,000 pounds of water, which is why a leveled base and a proper structure matter. The calculator shows the water weight along with the volume.
Related reading: How many gallons are in a pool?. For tanks and other containers, see the Tank Volume Calculator.
How do I calculate how many gallons are in my pool? Multiply the surface area by the average depth to get cubic feet, then multiply by 7.48 to convert to US gallons. For a 16 × 32 ft pool with an average depth of 5 ft that is 16 × 32 × 5 × 7.48 ≈ 19,150 gallons.
How do I find the average depth? Add the shallow-end depth to the deep-end depth and divide by two. This is accurate when the floor slopes steadily. If the pool has a long flat shallow area followed by a sudden drop, estimate the true average from the plan or measure each section separately.
How long does it take to fill a pool with a garden hose? Divide the volume by the flow rate. At about 9 gallons per minute, a 19,150-gallon pool takes around 35 hours, so roughly a day and a half. Time your own hose with a bucket, since pressure and hose size change the real rate.
How accurate is the kidney-shaped formula? It is an approximation that treats the curved outline as an average width. For a free-form pool the builder's volume figure, or a calculation split into simpler sections, will be closer.
Does the calculator account for the water level being below the top? Pools are normally filled several inches below the rim. For the most accurate figure, enter the depths measured to the water line rather than to the top of the wall.