Pool Volume Calculator
Find out how many gallons of water your pool holds. Pick your pool's shape, enter its size and depth, and get the volume in gallons, liters and cubic feet.
How to calculate pool volume
Pool volume is the pool's surface area times its average depth. That gives you cubic feet. One cubic foot holds 7.48 US gallons, so multiply by 7.48 to get gallons.
- Measure the length and width of the water surface in feet.
- Measure the depth at the shallow end and the deep end, from the water line to the floor.
- Add the two depths and divide by 2 to get the average depth.
- Multiply the surface area by the average depth to get cubic feet.
- Multiply the cubic feet by 7.48 to get gallons.
Rectangle pool formula
Gallons = length × width × average depth × 7.48
Example: A 16 × 32 ft pool is 3.5 ft deep at the shallow end and 8 ft at the deep end. The average depth is 5.75 ft. 16 × 32 × 5.75 × 7.48 = about 22,020 gallons.
Round pool formula
Gallons = diameter × diameter × average depth × 5.87
The 5.87 comes from π ÷ 4 × 7.48. Example: An 18 ft round pool filled to 3.5 ft holds 18 × 18 × 3.5 × 5.87 = about 6,660 gallons.
Oval pool formula
Gallons = length × width × average depth × 5.87
Example: A 15 × 30 ft oval pool filled to 3.5 ft holds 15 × 30 × 3.5 × 5.87 = about 9,250 gallons.
Kidney pool formula
Gallons = 0.45 × (A + B) × length × average depth × 7.48
A is the width of the wide end and B is the width of the narrow end. Example: A kidney pool 30 ft long, 15 ft and 10 ft wide, with an average depth of 5 ft, holds 0.45 × 25 × 30 × 5 × 7.48 = about 12,620 gallons. The 0.45 factor is a common estimate. For an exact number, split the pool into simple shapes and add them up.
Above-ground pool volume
Use the water depth, not the wall height. Above-ground pools are usually filled to the middle of the skimmer, about 6 inches below the top rail. A 48-inch wall holds about 42 inches of water, or 3.5 ft.
How to measure your pool
- Measure the inside of the pool at the water line, not the deck or coping.
- Measure depth from the water line to the floor, not from the top of the wall.
- For a round pool, measure straight across the center to get the diameter.
- For a freeform pool, measure the longest length and the widest width.
- Round each measurement to the nearest inch. Six inches is 0.5 ft.
How to find the average depth
If the floor slopes evenly from end to end, the average depth is the shallow depth plus the deep depth, divided by 2.
Many pools have a flat shallow end, a slope, and a flat deep end. A simple average can be off by more than 1,000 gallons for these pools. Choose "Shallow and deep end" in the calculator to work out each section on its own.
Even slope: 22,023 gallons
Flat shallow end, slope, flat deep end (16 ft, 6 ft, 10 ft): 20,407 gallons
The same pool holds about 1,600 fewer gallons when the deep end is short.
Pool volume for common sizes
These are US gallons, rounded to the nearest 10. Liters are rounded to the nearest 100.
| Pool | Size | Water depth | US gallons | Liters | Action |
|---|---|---|---|---|---|
| Round above-ground | 15 ft | 3.5 ft (48 in wall) | 4,630 | 17,500 | |
| Round above-ground | 18 ft | 3.5 ft (48 in wall) | 6,660 | 25,200 | |
| Round above-ground | 24 ft | 3.5 ft (48 in wall) | 11,840 | 44,800 | |
| Round above-ground | 24 ft | 3.8 ft (52 in wall) | 12,970 | 49,100 | |
| Oval above-ground | 15 × 30 ft | 3.5 ft (48 in wall) | 9,250 | 35,000 | |
| Rectangle in-ground | 12 × 24 ft | 3.5 to 5.5 ft | 9,690 | 36,700 | |
| Rectangle in-ground | 16 × 32 ft | 3.5 to 8 ft | 22,020 | 83,400 | |
| Rectangle in-ground | 20 × 40 ft | 3.5 to 8 ft | 34,410 | 130,300 | |
| Kidney in-ground | 30 ft, 15 and 10 ft wide | 5 ft average | 12,620 | 47,800 | |
| Olympic pool | 50 × 25 m (164 × 82 ft) | 2 m (6.6 ft) | 660,430 | 2,500,000 |
Pool volume in liters
One US gallon is 3.785 liters. Multiply gallons by 3.785 to get liters, or switch the result unit in the calculator. A 20,000-gallon pool holds about 75,700 liters.
If you measured in meters, length × width × depth gives cubic meters. One cubic meter is 1,000 liters.
Why your pool's volume matters
- Chemicals. Chlorine, shock, pH and alkalinity products list their doses per 10,000 gallons. If the volume is wrong, every dose is wrong too. Always follow the product label.
- Salt systems. A salt chlorine generator needs your pool's gallons to set the right amount of salt.
- Pump and filter. Many pool pros aim for one full turnover every 6 to 8 hours. Divide your gallons by the pump's flow in gallons per minute, then divide by 60 to get hours.
- Filling. A typical garden hose flows about 9 to 12 gallons per minute. At that rate a 20,000-gallon pool takes about 28 to 37 hours to fill.
- Covers and heaters. Solar covers are sized by surface area. Heaters are sized by gallons and surface area together. The calculator shows both.
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Frequently asked questions
How many gallons is my pool?
For a rectangle pool, multiply length × width × average depth × 7.48. For round and oval pools, multiply diameter × diameter (or length × width) × average depth × 5.87. You can also enter your sizes in the calculator above.
How many gallons are in an Olympic swimming pool?
An Olympic pool is 50 m long, 25 m wide and at least 2 m deep. At 2 m deep it holds 2,500 cubic meters of water. That is about 660,000 US gallons.
How long does it take to fill a pool?
Divide the pool's gallons by your hose's flow in gallons per minute, then divide by 60 to get hours. A typical hose fills a 20,000-gallon pool in 28 to 37 hours.
How do I find the volume of an irregular pool?
Split the pool into rectangles and circles. Find the volume of each part and add them together. For a kidney shape, the kidney option gives a close estimate.
Should I measure the water depth or the wall height?
Measure the water depth. The water sits below the top of the wall, so the wall height gives a number that is too high.
Does this work for hot tubs?
Yes. Use the round or rectangle shape. Seats take up space, so the real volume is a little lower than the result.
Are the results in US or UK gallons?
The calculator shows US gallons first. Switch the result unit to see UK gallons or liters. A UK gallon is about 20% larger than a US gallon.