Pool Volume Calculator - How Many Gallons Is My Pool?

Find out exactly how many gallons of water your swimming pool holds. Supports rectangular, circular, oval, and kidney shapes with sloping, flat, or hopper bottoms. Also includes chemical dosing, filter sizing, and heater requirements.

For kidney/irregular shapes — width at the narrower end

Rectangular: Volume (gal) = L × W × Avg Depth × 7.48
Circular: Volume (gal) = π × r² × Avg Depth × 7.48
Oval: Volume (gal) = π × (L/2) × (W/2) × Avg Depth × 7.48
Kidney: Volume (gal) = L × Avg Width × 0.85 × Avg Depth × 7.48

Filter Flow (GPM) = Pool Volume ÷ 480 min
Chlorine (oz) = Volume / 10000 × 8
A 40×20 ft rectangular pool, 3 ft shallow, 8 ft deep: Avg depth = 5.5 ft. Area = 800 sq ft. Volume = 800 × 5.5 × 7.48 = 32,912 gal. Filter = 32,912 ÷ 480 = 68.6 GPM. Shock = 32,912 ÷ 5,000 = 7 bags. Chlorine = 32,912 ÷ 10,000 × 8 = 26 oz.

How do I calculate the gallons in my pool?

The formula depends on shape. For rectangular pools: Length × Width × Average Depth × 7.48. For circular pools: π × Radius² × Depth × 7.48. For a 40×20 ft pool with 3-8 ft depth: average depth = 5.5 ft, volume = 40 × 20 × 5.5 × 7.48 = 32,912 gallons. Always use average depth, not maximum depth.

What is the average depth of a pool?

For a pool with a sloped bottom, average depth is (shallow end + deep end) ÷ 2. For a pool with a flat bottom (constant depth), use that single depth. For hopper-bottom pools (deep end only), average depth depends on the proportion of deep to shallow area, typically around 60% shallow depth.

How often should my pool water turn over?

The standard recommendation is one complete water turnover every 8 hours. Your pump and filter should be sized to circulate the entire pool volume within 8 hours. For a 30,000-gallon pool: 30,000 ÷ 480 minutes = 62.5 GPM minimum flow rate. Commercial pools may require 6-hour turnover.

How much chlorine do I need for my pool?

Initial chlorination requires about 7-8 ounces of chlorine per 10,000 gallons. For a 30,000-gallon pool: 24 ounces. Shock treatment typically needs 1 pound of shock per 5,000 gallons. Routine maintenance: maintain 1-3 ppm free chlorine, testing 2-3 times per week during swimming season.

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