About the Pool Volume Calculator
This pool volume calculator tells you how many gallons (and liters) of water your swimming pool, above-ground pool or hot tub holds. Choose the shape, enter the dimensions in feet and the shallow and deep end depths, and it calculates the surface area, average depth, cubic feet and total volume.
Knowing the exact volume matters every time you add chemicals: chlorine, shock, pH increaser, salt and algaecide doses are all specified per 10,000 gallons. It also helps you estimate how long a garden hose will take to fill the pool and size a pump that turns the water over in about 8 hours.
For pools with a sloped floor the calculator uses the average of the shallow and deep depths, which is accurate for a constant slope. For an above-ground or flat-bottom pool, enter the same value for both depths — measured to the water line, not the top of the wall.
With the default inputs, the pool volume is 22,023 US gal. Change any value above to recalculate instantly.
How to use the pool volume calculator
- 1Select the shape that best matches your pool or hot tub.
- 2Measure length and width (or diameter) across the water surface in feet.
- 3Measure water depth at the shallow and deep ends.
- 4Enter your hose flow rate if you want a fill-time estimate.
- 5Use the gallon figure when dosing chlorine, shock and other chemicals.
Formula and method
The surface area depends on the shape: length × width for a rectangle, π × radius² for a round pool, and π × (length ÷ 2) × (width ÷ 2) for an oval (an ellipse). Multiplying by the average depth gives the water volume in cubic feet, assuming the floor slopes evenly from the shallow end to the deep end.
One cubic foot holds 7.48052 US gallons, and one US gallon is 3.78541 liters. Fill time divides the volume by your hose flow rate in gallons per minute. Pools with a steep hopper or a large sun shelf may differ by a few percent.
- 7.48
- US gallons per cubic foot
- Surface area
- Water surface area in square feet
- Average depth
- Mean of shallow and deep water depths in feet
Worked examples
16 × 32 ft in-ground pool, 3.5–8 ft deep
The surface is 32 × 16 = 512 sq ft and the average depth is (3.5 + 8) ÷ 2 = 5.75 ft, giving 2,944 cubic feet. Multiplying by 7.48 gives about 22,023 gallons (83,365 liters), which takes roughly 37 hours to fill at 10 gallons per minute.
24 ft round above-ground pool, 4 ft of water
A 24 ft round pool has a surface area of π × 12² ≈ 452.4 sq ft. At a flat 4 ft of water that is about 1,810 cubic feet, or roughly 13,536 gallons.
15 × 30 ft oval pool, 4 ft deep
An oval 30 × 15 ft has an area of π × 15 × 7.5 ≈ 353.4 sq ft. With 4 ft of water it holds about 1,414 cubic feet, which is roughly 10,575 gallons.
Frequently asked questions
How many gallons are in a cubic foot of water?+
One cubic foot holds about 7.48 US gallons, or 28.3 liters. Multiply your pool volume in cubic feet by 7.48 to get gallons.
How do I measure the depth of a pool with a slope?+
Measure the water depth at the shallowest and deepest points and average them. This works well for an even slope; for a steep hopper-style deep end, the true volume may be slightly less.
How many gallons is a typical hot tub?+
Most home hot tubs hold roughly 300–500 gallons, and large six- to eight-seat spas can hold more. Molded seats and footwells displace water, so a simple box calculation overestimates; the manufacturer figure is the most accurate.
How long does it take to fill a pool with a hose?+
A garden hose delivers around 8–12 gallons per minute, so a 20,000-gallon pool takes roughly 28–42 hours. Using two hoses on separate spigots can nearly halve the time.
Why do I need to know my pool volume?+
Every pool chemical is dosed by volume. Overestimating wastes chemicals; underestimating leaves chlorine too low to sanitize. Knowing the volume also helps you size pumps, heaters and filters.