Pool volume formulas

Rectangular: Length × Width × Average Depth × 7.5 gallons/cu ft
Circular: π × Radius² × Average Depth × 7.5
Oval: Length × Width × 0.785 × Average Depth × 7.5
Kidney: (Length × Width A + Length × Width B) × 0.45 × Depth × 7.5

Chemical dosing context

Accurate pool volume is essential for correct chemical dosing. Overdosing chlorine can cause skin/eye irritation; underdosing allows bacterial and algae growth. A 10% volume error means a 10% error in every chemical calculation. Typical pools:

Small residential (12×24 ft): ~8,600 gallons
Medium residential (16×32 ft): ~18,700 gallons
Olympic (50m): ~660,000 gallons

How to measure irregular pools

For free-form, L-shaped, or kidney-shaped pools, break the shape into rectangles and sum the volumes. For an L-shape, measure the two rectangular sections separately. For kidney shapes, the standard formula is an approximation: true volume requires dividing the shape into several rectangular sections. When in doubt, add a 5–10% buffer to your chemical calculations.

Chemical dosing reference

Chemical	Typical dose per 10,000 gal	Purpose
Chlorine shock (granular)	1 lb	Sanitize / break chloramines
Algaecide	16 oz	Prevent algae growth
pH increaser (soda ash)	6 oz per 0.2 pH unit	Raise pH to 7.4–7.6
pH decreaser (muriatic acid)	10 oz per 0.2 pH unit	Lower pH to 7.4–7.6
Cyanuric acid (stabilizer)	13 oz to raise 10 ppm	Protect chlorine from UV

Always follow label directions; these are typical estimates only.

Turnover rate

The recommended practice is for all pool water to circulate through the filter at least once every 6–8 hours (daily turnover). To find the required pump flow rate in gallons per minute (GPM):

GPM = Pool Volume (gallons) ÷ Turnover Time (minutes)

For a 20,000-gallon pool with a target 8-hour turnover: 20,000 ÷ 480 = ~42 GPM minimum pump capacity. Use this to size or verify your pump and filter system.