How the above ground pool calculator works
Above ground pools have a flat floor, so there is no shallow end and deep end to average. The one number people get wrong is depth, because a 52 inch wall is filled to about 46 inches.
Round pools use the circle area formula. Oval pools use the ellipse formula, which is the same circle math stretched along the long side.
The formula, step by step
Gallons = Area (sq ft) x Water Depth (ft) x 7.48
- Round area = 3.14 x (diameter / 2) x (diameter / 2).
- Oval area = 3.14 x (length / 2) x (width / 2).
- Water depth in feet = inches of water divided by 12.
- Multiply area by depth for cubic feet, then by 7.48 for gallons.
Worked example
A 24 foot round pool is filled to 48 inches, which is 4 feet of water.
Area = 3.14 x 12 x 12 = 452 square feet. Volume = 452 x 4 = 1,809 cubic feet.
Gallons = 1,809 x 7.48 = 13,530 gallons, and that water weighs about 113,000 pounds.
Watch it done
This short video walks through the same job in real life, so you can match what you see on screen to what you do at the pool.
Tips before you start
Check the water line with a tape held against the inside wall. Guessing from the outside adds several inches and pushes your chemical doses too high.
Soft sided and frame pools lose depth as the walls bow out during the season. Re measure in midsummer if your chlorine seems to burn off faster than it used to.
Above Ground Pool Calculator FAQs
How many gallons is a 15 foot above ground pool?
A 15 foot round pool with 42 inches of water holds about 4,600 gallons. Fill depth is what changes the answer, so measure the water, not the wall.
Does the calculator work for oval frame pools?
Yes. Pick oval and enter the long side and the short side. The tool uses the ellipse area, which is around 21 percent less water than a rectangle of the same size.
How much does the water weigh?
Water weighs 8.34 pounds per gallon. A 24 foot round pool sits at roughly 56 tons, so the pad under it has to be level and firm.