Pool Volume Calculator
Calculate how many gallons of water your swimming pool holds. Works for rectangular, round and oval pools with a shallow end and a deep end.
By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.
Results
- Pool volume
- 15,989 gal
- At 7.48 gallons per cubic foot
- Volume of water
- 2,138 cu ft
- 79.2 cu yd
- Surface area
- 450 sq ft
- Average depth
- 4.75 ft
- (Shallow end + deep end) / 2
- Weight of water
- 66.7 tons
- At 8.34 lb per gallon
Pool Volume formula
Average depth = (Shallow depth + Deep depth) / 2
Rectangle area = Length x Width; Round area = 3.1416 x (Diameter / 2)²; Oval area = 3.1416 x (Length / 2) x (Width / 2)
Cubic feet = Area x Average depth
Gallons = Cubic feet x 7.48Worked example
A 16 x 32 ft rectangular in-ground pool, 3 ft in the shallow end and 8 ft at the deep end: average depth = (3 + 8) / 2 = 5.5 ft. 16 x 32 = 512 sq ft, and 512 x 5.5 = 2,816 cubic feet. 2,816 x 7.48 = 21,064 gallons.
A 24 ft round above-ground pool filled to 4 ft: area = 3.1416 x 12² = 452.4 sq ft. 452.4 x 4 = 1,809.6 cubic feet, and 1,809.6 x 7.48 = about 13,536 gallons.
Quick reference
| Pool | Average depth | Surface area | Gallons |
|---|---|---|---|
| 12 x 24 ft rectangle | 5 ft | 288 sq ft | 10,771 |
| 15 x 30 ft rectangle | 5 ft | 450 sq ft | 16,830 |
| 16 x 32 ft rectangle | 5 ft | 512 sq ft | 19,149 |
| 18 x 36 ft rectangle | 5 ft | 648 sq ft | 24,235 |
| 20 x 40 ft rectangle | 5 ft | 800 sq ft | 29,920 |
| 24 ft round | 4 ft | 452 sq ft | 13,535 |
| 27 ft round | 4 ft | 573 sq ft | 17,131 |
| 15 x 30 ft oval | 4 ft | 353 sq ft | 10,575 |
How to calculate pool volume
Measure the pool's length and width (or diameter) in feet and multiply for the surface area. Round pools use pi times the radius squared, and ovals use pi times half the length times half the width. Multiply the area by the average depth for cubic feet, then by 7.48 for gallons.
For a pool with a sloped bottom, the average of the shallow and deep end depths is close enough for chemical dosing. Kidney and freeform pools can be estimated by treating them as an oval or splitting them into two overlapping rectangles. Measure water depth, not wall height, since most pools are filled only to the skimmer line.
Why the number matters
Every chemical dose is based on gallons. Chlorine, shock, acid, alkalinity increaser and salt are all labeled per 10,000 gallons, so an estimate that is 20 percent off means every dose is 20 percent off. A common starting point is 1 lb of calcium hypochlorite per 10,000 gallons to raise free chlorine about 7 ppm, but always follow the product label and test the water.
Volume also sizes the pump, filter and heater. A pump should move the whole pool through the filter in 8 to 10 hours, and heaters are rated by how many degrees they raise a given volume per hour. Write the gallon figure down somewhere near the equipment pad.
Key facts
- One cubic foot of water is 7.48 US gallons and weighs 62.4 lb; one gallon weighs 8.34 lb.
- A 16 x 32 ft in-ground pool with an average depth of 5 ft holds about 19,000 gallons.
- One pound of 65% calcium hypochlorite raises free chlorine by about 7 ppm in 10,000 gallons of water.
- A pool pump should turn over the full volume of the pool in 8 to 10 hours; a 20,000 gallon pool needs about 40 gallons per minute.
- Filling a 20,000 gallon pool from a garden hose at 10 gallons per minute takes about 33 hours.
Frequently asked questions
How many gallons is a 16 x 32 pool?
With an average depth of 5 ft, 16 x 32 x 5 = 2,560 cubic feet, or about 19,150 gallons. A deeper pool with a 6 ft average holds about 23,000 gallons.
How many gallons is a 24 foot round pool?
At 4 ft of water, about 13,500 gallons. At 4.5 ft, about 15,200 gallons.
How do I find the average depth of my pool?
Add the shallow end depth to the deep end depth and divide by 2. A pool that runs from 3 ft to 8 ft has an average depth of 5.5 ft.
How much does the water in a pool weigh?
Water weighs 8.34 lb per gallon, so a 20,000 gallon pool holds about 167,000 lb, or 83 tons, of water.
Sources and references
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Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.