Pool Volume Calculator
Choose your pool shape, enter its size and the shallow and deep depths to see the number of gallons, liters and cubic feet of water it holds. The average depth handles a sloped floor.
How to use this pool volume calculator
- Pick the shape of your pool: rectangle, oval or round.
- Enter the size for that shape. Use feet. For a round pool, enter the diameter.
- Enter the depth at the shallow end and at the deep end. For a flat floor, use the same number twice.
- If the water normally sits below the full depth, enter that gap in inches. Leave it at 0 if you fill to the top.
- Press Calculate to see the volume in gallons, liters and cubic feet. Use Copy result to keep it for chemical dosing or a water order.
How to calculate how many gallons are in a pool
The volume of a pool is its surface area times its average depth. The calculator then converts cubic feet to gallons.
- Rectangle area = length x width
- Oval area = pi x length x width / 4, where pi is about 3.14159
- Round area = pi x diameter x diameter / 4
- Average depth = (shallow depth + deep depth) / 2 – water level offset (in feet)
- Cubic feet = area x average depth
- US gallons = cubic feet x 7.48052, and liters = cubic feet x 28.3168
Worked example
A rectangular pool is 32 ft long and 16 ft wide. The shallow end is 3.5 ft deep and the deep end is 8 ft deep. The average depth is (3.5 + 8) / 2 = 5.75 ft. The surface area is 32 x 16 = 512 sq ft. The volume is 512 x 5.75 = 2,944 cubic feet. In gallons that is 2,944 x 7.48052 = 22,023 gallons, or about 83,365 liters.
A round pool 24 ft across and a flat 4 ft deep has an area of 452.4 sq ft, a volume of 1,809.6 cubic feet and about 13,536 gallons.
Assumptions & limits
- The floor slopes evenly from the shallow end to the deep end, so the average depth is the mean of the two. A pool with a steep drop or a deep hopper holds a different amount.
- The shape is a clean rectangle, oval or circle. Kidney, freeform and L-shaped pools need to be split into parts.
- Steps, benches and tanning ledges take up space and are not subtracted, so the real volume is a little less.
- One US gallon is 0.133681 cubic feet. Imperial gallons are not used.
- Use the result as a guide and read the label of any chemical product for its own instructions.
Frequently asked questions
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. A 32 ft by 16 ft pool with a 5.75 ft average depth holds about 22,000 gallons.
How do I find the average depth?
Add the shallow end depth and the deep end depth and divide by 2. This works well for a floor that slopes evenly.
How do I calculate the volume of a round pool?
Multiply pi by the radius squared by the average depth, then convert to gallons. The calculator uses the diameter and does this for you.
How many liters are in a gallon of pool water?
One US gallon is about 3.785 liters, and one cubic foot of water is about 28.3 liters.
Why might my real volume differ?
Steps, benches, a hopper and a water level below the top all change the volume. The calculator gives a close estimate, not an exact figure.
Why does pool volume matter?
Chemical dosing, heater sizing and filling costs all depend on the volume of water. Check product labels for their instructions.
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Last updated: November 2026