BuildCalc Pro

Pool Volume Calculator

Calculate the water volume of any swimming pool shape. Get results in gallons, liters, and cubic feet with chemical dosing estimates.

How to Use This Calculator

1. Select Imperial (feet) or Metric (meters) units. 2. Choose your pool shape: rectangular, circular, oval, or kidney. 3. Enter pool dimensions (length/width or diameter depending on shape). 4. Enter shallow end and deep end depths — use the same value for constant depth. 5. Click Calculate to see volume in multiple units plus chemical estimates.

How to Calculate Swimming Pool Volume Accurately

Knowing your pool's exact water volume is essential for proper chemical treatment, heater sizing, pump selection, and estimating fill costs. An incorrect volume estimate leads to over- or under-dosing chemicals, which can damage equipment, irritate swimmers, or allow algae growth.

For rectangular pools, the formula is simple: Length × Width × Average Depth × 7.48 = gallons. The 7.48 factor converts cubic feet to gallons. Average depth is calculated as (shallow end + deep end) ÷ 2. A 30×15-foot pool with 4-foot shallow and 8-foot deep end holds about 20,196 gallons.

Circular pools use the formula: π × radius² × average depth × 7.48. For oval pools, use π × (length/2) × (width/2) × average depth × 7.48. Kidney and freeform pools are trickier — multiply the length × width × average depth × 7.48 × 0.675 (a shape correction factor).

Pool volume directly determines chemical dosing. Chlorine, pH adjusters, algaecides, and shock treatments are all dosed per 10,000 gallons. A 20,000-gallon pool needs exactly twice the chemicals of a 10,000-gallon pool. Using the wrong volume leads to either ineffective treatment or dangerous over-chlorination.

Filling a pool typically costs $50-$200+ depending on volume and local water rates. A garden hose delivers about 540 gallons per hour, so filling a 20,000-gallon pool takes roughly 37 hours. Many pool owners use water delivery trucks for faster fills at $200-$600 per truckload (6,000 gallons).

Frequently Asked Questions

How many gallons is a typical swimming pool?

A small residential pool (12×24 ft) holds about 8,600 gallons. A medium pool (16×32 ft) holds about 19,200 gallons. A large pool (20×40 ft) holds about 30,000 gallons. Olympic pools hold 660,000 gallons.

How long does it take to fill a pool?

A standard garden hose delivers about 540 gallons per hour (9 GPM). Filling a 20,000-gallon pool takes about 37 hours. A water delivery truck can deliver 6,000 gallons at once for $200-$600, significantly reducing fill time.

How much chlorine do I need for my pool?

To raise free chlorine by 1 ppm, add 0.013 oz of chlorine per gallon (or about 2 oz per 10,000 gallons of a standard chlorine product). Ideal free chlorine is 1-3 ppm. For shock treatment, aim for 10 ppm temporarily.

How much does it cost to fill a pool with water?

Water costs vary by location but average $4-$6 per 1,000 gallons. Filling a 20,000-gallon pool costs roughly $80-$120 in water charges. Some areas charge sewer surcharges on water use — contact your utility about pool fill credits.