How the kidney pool volume calculator works
Add width A and width B, multiply by 0.45, then multiply by the length. The 0.45 factor accounts for the concave side that a plain rectangle would ignore.
That area is multiplied by average depth. Kidney pools usually slope, so enter a shallow and a deep end reading.
The formula
Volume = 0.45 x (width A + width B) x length x average depth
Measure: Two widths, length, average depth.
Worked example
A kidney with a 16 foot lobe, a 10 foot waist and a 30 foot length gives 0.45 x 26 x 30, or 351 square feet.
At an average depth of 5 feet that is 1,755 cubic feet, close to 13,128 gallons or 49,690 litres.
Tips before you measure
Take both widths at right angles to the long axis of the pool, not diagonally.
If your pool has a deep hopper under the widest lobe, the average depth method still works because that lobe carries most of the water.
Kidney pool volume FAQs
Where do I measure the two widths?
Width A is across the widest lobe. Width B is across the pinched waist where the pool curves inward.
Why the 0.45 factor?
It converts the two widths and length into the real curved footprint. It is the standard industry factor for kidney pools.
How accurate is the result?
Within about 5 percent for a typical kidney. Sharper curves push the estimate slightly higher than the true volume.
Other pool shapes
Not quite the right outline? The main pool volume calculator covers all 20 shapes with the same units and formulas.