Calculate the water volume of a pool by shape and depth.
Pool volume is surface area times average depth, with a shape factor to account for the plan not being a rectangle: 1.0 for rectangular, 0.893 for an oval and 0.785 for a circle, which is simply pi over four. Average depth for a pool with a shallow and a deep end is the mean of the two, which is accurate for a constant slope and slightly generous for a pool with a flat shallow shelf and a sudden hopper. Converting cubic feet to gallons uses 7.48052. Getting this number right matters because every chemical dose is per 10,000 gallons — an error of 15% in volume is an error of 15% in every chlorine, acid and stabiliser addition for the life of the pool.
Pool Volume
Volume cu ft = length x width x shape factor x (shallow + deep) / 2; gallons = cu ft x 7.48052; litres = gallons x 3.78541
Volume figures are for dosing and equipment planning. Pool chemical handling and water safety carry real risks — follow product instructions and local health regulations, and never mix chemicals.
About 21,500 gallons with a 3.5 to 8 ft slope, giving an average depth of 5.75 ft. A flat 4 ft depth in the same footprint is around 15,300.
Every chemical dose is expressed per 10,000 gallons. Underestimating volume means chronic under-chlorination; overestimating means wasted chemicals and pH swings.