Pool Volume Calculator
Find your swimming pool water volume in gallons and liters from a few measurements.
For a pool with a single, even depth, enter the same number in both depth fields.
This calculator runs entirely in your browser. Your measurements are never uploaded anywhere.
How to use this tool
Pick your pool shape at the top: rectangular, round, or oval. Enter the surface measurements in feet. For a rectangle that is length and width, for a round pool it is the diameter, and for an oval it is the long and short diameters. Then measure the water depth at the shallow end and the deep end and enter both. If your pool has one even depth all the way across, type the same value in both depth boxes. Press Calculate Volume and this pool gallon calculator returns the pool water volume in both gallons and liters, along with the average depth it used.
The formula and how it works
Rectangular pool: gallons = length x width x average depth x 7.48
Round pool: gallons = diameter x diameter x average depth x 5.9
Oval pool: gallons = long x short x average depth x 5.9
Liters = gallons x 3.785412
Water volume is just the surface area of the pool multiplied by how deep the water is. A rectangle's area is length times width. Because most pools slope from a shallow end to a deep end, we use the average of the two depths, which is accurate for a steady, even slope. One cubic foot of water holds about 7.48 US gallons, so multiplying the cubic feet by 7.48 gives the swimming pool capacity in gallons. Round and oval pools use a 5.9 multiplier, which already folds in the area math for a circle or ellipse so you only supply the diameters. To convert to metric, one US gallon equals 3.785412 liters.
A real example
Say you have a rectangular pool that is 32 feet long and 16 feet wide. The shallow end is 3 feet deep and the deep end is 8 feet deep. The average depth is (3 + 8) / 2 = 5.5 feet. Multiply 32 x 16 x 5.5 to get 2,816 cubic feet of water. Multiply by 7.48 and you get about 21,063 gallons, which is roughly 79,732 liters. That figure tells you how much water you need to fill the pool and helps you dose chemicals correctly based on the pool depth and volume.
Note: This is an estimate for educational and planning use. Sloped floors, steps, tanning ledges, and rounded corners change the true number. For exact chemical dosing or equipment sizing, confirm with a pool professional.
Common questions
How do I find pool water volume in gallons?
Measure the pool's length and width (or diameter) and the depth at both the shallow and deep ends, all in feet. Multiply the surface area by the average depth to get cubic feet, then multiply by 7.48 to convert to US gallons. This tool does that math for you and also shows liters.
Why does the calculator use the average depth?
Most pools are not the same depth everywhere, so a single depth would be wrong. Averaging the shallow and deep ends gives an accurate result for a pool floor that slopes evenly between the two. If your pool is one flat depth, just enter that same number twice.
Where do the 7.48 and 5.9 multipliers come from?
One cubic foot of water holds about 7.48 US gallons, which is why rectangular pools use that factor after the length-by-width area. For round and oval pools, the 5.9 factor already includes the area formula for a circle or ellipse, so you only enter the diameters and the depth.
How accurate is this swimming pool capacity estimate?
It is very close for standard pool shapes with an even slope. It does not account for steps, benches, tanning ledges, or rounded edges, which slightly reduce the real volume. Treat the result as a strong estimate for filling and chemical planning.
Can I convert the result to liters?
Yes. The tool shows liters automatically. One US gallon equals 3.785412 liters, so the gallon figure is multiplied by that number to give the metric volume.