Calculate the volume of an oval pool in gallons or litres using the correct ellipse formula. Free calculator.
If you already know the pool’s surface area, you can enter it directly instead of the two axes. Switch to “I know my surface area”, type in the square footage, and set your average depth.
Length × Width × π ÷ 4 × Average Depth × 7.48 = US gallons
A 30 ft × 15 ft oval pool at 4 ft average depth: 30 × 15 × 0.7854 × 4 × 7.48 ≈ 10,575 gallons.
This calculator uses the precise cubic-foot-to-gallon value (about 7.48 US gallons per cubic foot) for your oval pool and lets you switch between US gallons, imperial gallons, litres, and cubic metres.
You will need these measurements:
A 30 ft × 15 ft oval averaging 4.5 ft: π × 15 × 7.5 × 4.5 = 1,590 cubic feet, then × 7.48 ≈ 11,897 US gallons.
Approximate capacity at 4 ft average depth, computed with this calculator. Your exact number depends on your real depth.
| Pool size | US gallons |
|---|---|
| 12 × 24 ft oval | 6,768 |
| 15 × 30 ft oval | 10,575 |
| 16 × 32 ft oval | 12,032 |
| 18 × 33 ft oval | 13,959 |
| 18 × 36 ft oval | 15,228 |
The common oval mistake is treating it like a rectangle and multiplying length by width — that overstates the volume by about 21%, because an ellipse fills less area than its bounding box. The correct surface area is π × (length ÷ 2) × (width ÷ 2), using the two axes as the major and minor radii. Measure the full length along the long axis and the full width at the widest point of the short axis, both at the waterline. Oval above-ground pools, like round ones, are usually uniform depth and filled below the rim, so use the actual water depth. Oval in-ground pools may slope, in which case average the shallow and deep ends as you would for a rectangle.
The method behind this calculator draws on established standards, peer-reviewed academic sources, and reference values:
Results are planning estimates. Where a figure depends on your local rates, codes, or site conditions, confirm with the cited authority or a qualified professional.