L-Shaped Pool Volume Calculator

Already know your surface area?

If your pool plans list the total surface area, you can skip adding up the two rectangular sections. Switch to “I know my surface area”, enter the square footage, set your average depth, and get the gallons directly.

The formula

Section 1 volume + Section 2 volume = total gallons

Worked example

An L-shaped pool with a 20 ft × 10 ft × 8 ft section and a 10 ft × 10 ft × 6 ft section holds (1,600 + 600) × 7.48 ≈ 16,456 gallons. Add the second section below to model yours.

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

How to calculate L-shaped pool volume step by step

You will need these measurements:

The dimensions of each simple section (rectangle, circle, or oval)
The average water depth of each section, in feet

Split the L into two rectangles. An L-shaped pool is two rectangles. Divide it into a long rectangle and a short rectangle so the two pieces don't overlap.
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.
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

An L made of a 30 ft × 15 ft section and a 15 ft × 10 ft section, both 5 ft deep: (30 × 15 × 5) + (15 × 10 × 5) = 3,000 cubic feet, then × 7.48 ≈ 22,442 US gallons.

Splitting an L-shaped pool correctly

An L-shaped pool is two rectangles joined at a right angle, and the only trick is dividing them so they don't overlap. Draw a line that extends one of the inner edges, splitting the L into a longer rectangle and a shorter one; measure each rectangle's length and width separately, with no shared area counted twice. Calculate each rectangle's volume using its own average depth — the two arms of an L often have different depths, such as a shallow lounging leg and a deeper swimming leg — then add them. Counting the corner region in both rectangles is the usual error and inflates the total, so be deliberate about where one rectangle ends and the other begins.

Sources & references

The method behind this calculator draws on established standards, peer-reviewed academic sources, and reference values:

Composite-area method — the pool is split into two rectangular sections whose areas are added
U.S. customary unit conversions (NIST reference values) — 1 ft³ = 7.4805 US gallons; water weighs ≈ 8.34 lb per gallon
See the exact working on our formula reference and the reasoning on our methods page.

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.

Related calculators & guides

Rectangle pool volumeLength × width × depth Round pool volumeCircular pools & spas Oval pool volumeEllipse footprint Guide: Measure volume for any shapeMaster formula & depth

Questions

Common answered

Yes. Instead of measuring both legs of the L, switch to “I know my surface area”, enter the total square footage from your plans, and add your average depth. Volume is surface area × average depth × 7.48.

Split the L into two non-overlapping rectangles, calculate each one's volume with its own average depth, and add them together. The combiner above lets you enter both sections.

Extend one of the inner edges to cut the L into a longer rectangle and a shorter one, making sure the corner area is counted in only one of them.

Yes, and they often do — one leg may be shallow and the other deep. Use each rectangle's own average depth, then add the two volumes.

Counting the corner area in both rectangles, which double-counts that water and overstates the volume. Split the shape so no area belongs to both parts.