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Pool Volume Calculator

Volume of a freeform or lagoon pool

Calculate the volume of a freeform, lagoon, or irregular pool by combining simple sections. Free section-by-section calculator with a live total.

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

The formula

Section 1 + Section 2 + … = total volume (each section × its own depth)

Worked example

True freeform pools rarely fit one formula, so break yours into simple shapes — rectangles, circles, ovals — give each part its own size and depth, and the calculator adds them into one total. Use “Add section” below to combine as many parts as your pool needs; the running total and shareable link update live. For a classic single-basin kidney shape, the dedicated kidney calculator is simpler.

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

How to calculate freeform or lagoon pool volume step by step

You will need these measurements:

  1. Break the pool into simple sections. A freeform or lagoon pool is easiest to measure as a few simple shapes — rectangles, circles, ovals — that together approximate the outline. Add a section here for each piece.
  2. Calculate each section's volume. For each piece, find its area, multiply by that section's average depth to get cubic feet. This calculator does it for you as you add sections.
  3. Add the sections and convert. Add the cubic feet of all sections, then multiply by 7.48 for US gallons. The running total updates automatically above.
Worked example

A lagoon split into a 20 ft × 14 ft rectangle and a 12 ft-diameter circle, both 4.5 ft deep: (20 × 14 × 4.5) + (π × 6² × 4.5) ≈ 1,769 cubic feet, then × 7.48 ≈ 13,233 US gallons.

Estimating a freeform or lagoon pool

Freeform and lagoon pools have no single formula because their outlines are irregular by design. The reliable approach is to break the pool into simple shapes you can measure — a rectangle for the main body, a circle or oval for a rounded end, a triangle for a tapering corner — calculate each, and add the volumes. Choose divisions that don't overlap and that follow the real outline closely; more, smaller sections give a better approximation than one forced shape. Average the shallow and deep depths within each section. This section-by-section method is exactly how the combiner above works, and it's more accurate for an organic shape than applying a single rectangle or oval formula to the whole thing.

Questions

Common answered

Break it into simple shapes — rectangles, circles, ovals — calculate each section's volume, and add them up. The combiner above does this as you add sections.
Freeform outlines are irregular and unique, so no single formula fits. Splitting the pool into measurable shapes and summing them is the accurate approach.
Enough to follow the real outline without overlapping. A main rectangle plus one or two rounded ends is often enough; more sections improve accuracy for very organic shapes.
Yes. Treat each section like its own small pool and average its shallow and deep depths before adding the volumes together.