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Pool Volume Calculator

Volume of a oval pool

Calculate the volume of an oval pool in gallons or litres using the correct ellipse formula. Free calculator.

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

The formula

Length × Width × π ÷ 4 × Average Depth × 7.48 = US gallons

Worked example

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.

How to calculate oval pool volume step by step

You will need these measurements:

  1. Measure the long axis, short axis, and depth. Measure the full length (long axis) and full width (short axis) in feet, plus the average water depth.
  2. Find the elliptical surface area. Surface area = π × (Length ÷ 2) × (Width ÷ 2). This is the ellipse area, not length × width.
  3. Multiply by depth, then convert. Volume in cubic feet = surface area × depth. Multiply by 7.48 for US gallons.
Worked example

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.

Common oval pool sizes

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

Pool sizeUS gallons
12 × 24 ft oval6,768
15 × 30 ft oval10,575
16 × 32 ft oval12,032
18 × 33 ft oval13,959
18 × 36 ft oval15,228

Why oval pools aren't length times width

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.

Questions

Common answered

A 15 ft × 30 ft oval holds roughly 12,700 gallons at 4 ft of water. Enter your real water depth above for an exact figure.
That treats the oval as a rectangle and overstates it by about 21%. An ellipse covers less area than its bounding box, so the formula uses π × half the length × half the width.
Measure the full length along the long axis and the full width at the widest point of the short axis, both at the waterline. Those two axes drive the ellipse area.
If it slopes, yes — average the shallow and deep ends. Most oval above-ground pools are a single uniform depth, so the average equals that one depth.
No. A true oval (ellipse) curves continuously, while a stadium or Roman shape is a rectangle with semicircular ends. Use the Roman calculator for the latter — the area formulas differ.