All calculators free & instant No signup · Gallons, litres & m³
Pool Volume Calculator

Volume of a kidney pool

Calculate the volume of a kidney-shaped pool using the industry-standard two-width formula. Free, instant, in gallons or litres.

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

The formula

(Width A + Width B) × Length × 0.45 × Average Depth × 7.48 = US gallons

Worked example

Measure the full length, the widest bulge (Width A), and the narrowest bulge (Width B). A pool 20 ft long with Width A 10 ft and Width B 8 ft at 8 ft average depth holds (10 + 8) × 20 × 0.45 × 8 × 7.48 ≈ 9,694 gallons. The 0.45 multiplier is the industry standard that accounts for the kidney's curved area — the same constant Inch Calculator and other major tools use.

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

How to calculate kidney pool volume step by step

You will need these measurements:

  1. Measure both widths, length, and depth. A kidney pool has two different widths. Measure the widest bulge (Width A), the narrowest bulge (Width B), the overall length, and the average depth.
  2. Apply the kidney area formula. Surface area = 0.45 × (Width A + Width B) × Length. The 0.45 factor accounts for the curved kidney outline.
  3. Multiply by depth, then convert. Volume in cubic feet = surface area × depth. Multiply by 7.48 for US gallons.
Worked example

A kidney pool with widths 16 ft and 10 ft, length 30 ft, 5 ft deep: 0.45 × (16 + 10) × 30 × 5 = 1,755 cubic feet, then × 7.48 ≈ 13,128 US gallons.

Common kidney pool sizes

Approximate capacity at 5 ft average depth, computed with this calculator. Your exact number depends on your real depth.

Pool sizeUS gallons
16 × 30 ft kidney13,633
16 × 34 ft kidney15,451
18 × 36 ft kidney18,178
20 × 38 ft kidney21,106

Measuring the two widths of a kidney pool

A kidney pool is defined by two different widths, and getting both is what makes the estimate accurate. Width A is the widest bulge across the larger lobe; Width B is the narrower width across the smaller lobe near the waist. Measure the length down the long axis of the pool. The industry-standard formula — 0.45 × (Width A + Width B) × length — uses the 0.45 factor to account for the curved, pinched kidney outline, which fills less area than a rectangle of the same length and average width. This is the same approximation used by major pool references, so it matches the figures pool professionals work from. As with any in-ground pool, average the shallow and deep depths rather than using a single number.

Questions

Common answered

Use 0.45 × (Width A + Width B) × length to get the surface area, multiply by average depth for cubic feet, then by 7.48 for gallons. The 0.45 factor handles the curved kidney outline.
Width A is the widest bulge across the larger lobe; Width B is the narrower width across the smaller lobe. A kidney pool has two distinct widths, which is why both are needed.
The curved, pinched kidney shape covers less area than a plain rectangle of the same length and average width. The 0.45 factor is the industry-standard adjustment for that outline.
A kidney pool around 16 ft by 30 ft holds roughly 13,000 gallons at 5 ft average depth. Your exact figure depends on both widths and your depth — enter them above.
It's a close, widely-used approximation rather than an exact integral of the curve, since real kidney outlines vary. It matches the figures used by major pool calculators and professionals.