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Pool Volume Calculator

Volume of a round pool

Calculate the volume of a circular or round above-ground pool in gallons or litres. Free instant calculator.

✓ Sloped & deep-end floors ✓ Gallons, litres & m³ ✓ Combine irregular shapes

The formula

π × radius² × Average Depth × 7.48 = US gallons

Worked example

A 24 ft round pool filled to 4 ft of water: radius 12 ft, so π × 12² × 4 × 7.48 ≈ 13,531 gallons. Remember to use the water depth, not the full wall height.

This calculator uses the precise cubic-foot-to-gallon value (about 7.48 US gallons per cubic foot) for your round pool and lets you switch between US gallons, imperial gallons, litres, and cubic metres.

How to calculate round pool volume step by step

You will need these measurements:

  1. Measure diameter and water depth. Measure the diameter (straight across the widest point) and the actual water depth in feet — round pools are usually filled below the rim.
  2. Find the radius and the surface area. Radius = diameter ÷ 2. Surface area = π × radius² (π ≈ 3.14159).
  3. Multiply by depth, then convert. Volume in cubic feet = surface area × depth. Multiply by 7.48 for US gallons.
Worked example

A 24 ft round pool filled to 4 ft: radius 12 ft, π × 12² × 4 = 1,810 cubic feet, then × 7.48 ≈ 13,536 US gallons.

Common round pool sizes

Approximate capacity at 4 ft average depth, computed with this calculator. Your exact number depends on your real depth.

Pool sizeUS gallons
15 ft round5,288
18 ft round7,614
21 ft round10,364
24 ft round13,536
27 ft round17,132

Water depth vs wall height on round pools

The mistake that throws off round-pool volume most is using the wall height instead of the actual water depth. A round above-ground pool with a 52-inch wall is rarely filled to the top — water usually sits around 46–48 inches, below the skimmer cut-out. Always measure from the floor to the real waterline. Measure the diameter straight across the widest point through the center; measuring a chord that misses the center understates the diameter and, because area depends on the radius squared, even a small diameter error has an outsized effect on the result. Round pools are uniform depth, so there is no shallow-and-deep average to worry about — just one honest water depth.

Questions

Common answered

A 24 ft round pool holds about 13,500 gallons at 4 ft of water. Filled deeper or shallower changes it proportionally — enter your actual water depth above for your number.
Always the water depth. A 52-inch-wall pool typically holds only about 46–48 inches of water, since it's filled to just below the skimmer. Using the full wall height overstates the volume.
Measure straight across the widest point, passing through the center. A line that misses the center comes up short, and because volume depends on the radius squared, that error is magnified in the result.
The surface of a round pool is a circle, whose area is π × radius². Squaring the radius is what captures the circular area; multiplying by depth then gives the volume.
Yes — both use π × radius² × water depth. Above-ground pools just tend to be uniform depth and filled below the rim, so the water depth is the figure to measure.