Pool Water Volume Calculator
Start with the shape at the waterline
Use the inside dimensions of the water surface. A rectangular pool has surface area length × width. A round pool uses π × (diameter ÷ 2)². An elliptical pool uses π × length × width ÷ 4. Multiply that area by the appropriate average water depth to estimate volume.
For a flat bottom, enter one constant water depth. For an even slope, enter the shallow and deep depths; their average is (shallow + deep) ÷ 2. These simplified models assume vertical walls and the stated floor shape. They do not measure an irregular pool automatically.
Example: a 20-by-10-foot pool
A rectangular pool measuring 20 ft × 10 ft with an even slope from 4 ft to 6 ft has an average water depth of 5 ft. Its volume is 20 × 10 × 5 = 1,000 ft³, or about 7,480.519 US gallons, 28,316.847 liters, and 28.317 m³. The starting measurements in the calculator show this example; replace them with your pool measurements.
Calculate a shelf, slope, and deep section separately
For a rectangular pool with a flat shallow shelf, a straight sloping floor, and a flat deep section, choose the segmented floor option. All three sections must span the same pool width. Their lengths add up to the total length: the deep-section length is whatever remains after subtracting the shelf and slope.
For example, take a pool 10 m long and 3 m wide, with a 2 m shelf at 1 m depth, a 4 m slope from 1 m to 2 m, and a remaining 4 m deep section at 2 m depth. The section volumes are 6 + 18 + 24 = 48 m³. Treating the whole pool as one slope would give only 10 × 3 × 1.5 = 45 m³. The breakdown shows that 3 m³ difference.
A zero shelf or slope length is allowed when that section is absent. Shelf plus slope cannot exceed the total pool length. For other profiles, divide the pool into suitable simple volumes using measurements or plans; an endpoint average alone cannot describe every floor.
Use the estimate with its limits
Small measurement errors can change a large pool's volume substantially. Curved walls, benches, steps, unusual slopes, and shallow ledges are not subtracted here. The result estimates water volume for the geometry you enter; it does not select chemical doses, pumps, heaters, or structural designs.
Changing the measurement unit converts valid dimensions already entered. Clear measurements empties the fields and removes the result. The calculation runs in your browser; tool analytics do not include your dimensions or volume results.
Frequently asked questions
How do I calculate the volume of water in my pool?
Choose the pool shape and floor profile, then enter the inside dimensions and actual water depths in feet or meters. For a rectangle with a flat floor, volume is length × width × water depth. For an even slope, use the average of the shallow and deep water depths. The results show US gallons, liters, cubic meters, and Imperial gallons separately.
Which measurements do I need for a round or oval pool?
For a round pool, enter its full diameter, not its radius. For an oval modeled as an ellipse, enter its full length and full width. Measure at the waterline. Round-ended rectangles, kidney shapes, and other irregular outlines are not the same as ellipses, so these formulas may not fit them.
When is average depth misleading?
A simple average of two end depths works for a flat floor or an even slope across a symmetric pool footprint. A long deep section and a short shallow shelf need different weighting. For a rectangular pool, choose Shelf → slope → deep section and enter the shelf and slope lengths. The calculator derives the remaining deep-section length and adds the three volumes.
Do I measure wall height or water depth?
Measure from the current water surface down to the floor. The empty space above the water does not contribute to water volume. This calculator assumes vertical walls and does not subtract steps, benches, ledges, or other objects from the estimate.
Are US gallons and Imperial gallons the same?
No. One US liquid gallon is 3.785411784 liters, while one Imperial gallon is 4.54609 liters. The same pool therefore has different numerical totals in these units. This tool labels both explicitly; liters and cubic meters are also shown.
Why does another pool calculator give a slightly different answer?
Some pool calculators use rounded factors such as 7.5 US gallons per cubic foot. This tool uses the defined foot and gallon conversions before rounding the displayed result. Differences in shape assumptions, water depth, benches, or the floor profile can matter much more than that rounding difference.