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Pool Volume Calculator

Volume of a triangular pool

Calculate the volume of a triangular pool in gallons or litres. Free instant calculator with sloped-floor support.

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

The formula

(Length × Width) ÷ 2 × Average Depth × 7.48 = US gallons

Worked example

A triangular pool with a 20 ft base and 10 ft height at 6 ft average depth: (20 × 10) ÷ 2 × 6 × 7.48 ≈ 4,488 gallons.

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

How to calculate triangular pool volume step by step

You will need these measurements:

  1. Measure base, height, and depth. For a triangular pool, measure the base and the perpendicular height (not the slanted side), plus the average water depth, all in feet.
  2. Find the triangular area. Surface area = ½ × Base × Height.
  3. Multiply by depth, then convert. Volume in cubic feet = surface area × depth. Multiply by 7.48 for US gallons.
Worked example

A triangular pool with a 24 ft base and 20 ft height, 4.5 ft deep: ½ × 24 × 20 × 4.5 = 1,080 cubic feet, then × 7.48 ≈ 8,079 US gallons.

Measuring a triangular pool

Triangular pools are less common but show up in tight or angular yards. The area is ½ × base × height, where the height is the perpendicular distance from the base to the opposite point — not the length of a slanted side. This is the measurement people most often get wrong: if you measure along a diagonal edge instead of the perpendicular, the area comes out too large. Pick one side as the base, then measure straight across to the far corner at a right angle to that base. As with any pool, average the shallow and deep depths if the floor slopes. For irregular four-sided or angular pools, splitting the shape into triangles and rectangles and adding them is more accurate than forcing a single formula.

Questions

Common answered

Find the area with ½ × base × height, multiply by average depth for cubic feet, then by 7.48 for gallons. The height must be the perpendicular distance to the far corner, not a slanted side.
The height is the straight, perpendicular distance from your chosen base to the opposite point — measured at a right angle to the base, not along a diagonal edge.
A triangle fills exactly half of the rectangle that would enclose its base and height, so its area is half of base × height.
Split it into triangles and rectangles, calculate each piece, and add the volumes. The freeform calculator lets you combine sections this way.
Yes, if the floor slopes. Average the shallow and deep depths just as you would for any other shape.