Pool Volume Calculator
Calculate the total water volume in gallons for rectangular, circular, or oval pools using pool dimensions. Essential for sizing pumps, dosing chemicals, and planning pool fills.
About this calculator
Pool volume is calculated by multiplying the pool's surface area by its average depth, then converting cubic feet to gallons using the factor 7.48 gallons per cubic foot. The formulas by shape are: Rectangular: Volume = length × width × depth × 7.48. Circular: Volume = π × (diameter/2)² × depth × 7.48. Oval: Volume = π × (length/2) × (width/2) × depth × 7.48. The oval formula treats the pool as an ellipse, which closely approximates most oval pool shapes. Accurate volume is critical for calculating chemical dosing—too little sanitizer leaves water unsafe, while too much wastes money and irritates swimmers. Pool pump sizing also depends on volume to ensure proper turnover rates.
How to use
You have a rectangular pool that is 30 feet long, 15 feet wide, and 5 feet of average depth. Volume in cubic feet = 30 × 15 × 5 = 2,250 ft³. Convert to gallons: 2,250 × 7.48 = 16,830 gallons. Now select 'rectangular' in the shape menu, enter 30 for length, 15 for width, and 5 for depth. The calculator returns approximately 16,830 gallons—enough to properly size your pump and calculate chlorine doses.
Frequently asked questions
Why do I need to know my pool's volume in gallons?
Knowing your pool's volume is essential for correct chemical dosing—chlorine, pH adjusters, algaecides, and shock treatments are all dosed per 10,000 gallons. Underdosing leads to unsafe water, while overdosing wastes chemicals and can irritate skin and eyes. Pool pump and filter systems are also rated by gallons per hour, and your pool needs at least one full water turnover every 8 hours. Volume calculations help ensure all these systems work correctly together.
How do I calculate the average depth of a pool with a sloped bottom?
For pools with a shallow end and a deep end, the average depth is simply (shallow end depth + deep end depth) / 2. For example, a pool that is 3 feet at one end and 8 feet at the other has an average depth of (3 + 8) / 2 = 5.5 feet. This average is accurate for volume calculations when the slope is gradual and consistent. If your pool has a flat bottom with a single step or ledge, you may need to calculate each section separately and add them.
How many gallons does a standard backyard pool hold?
A typical rectangular backyard pool measuring 16 × 32 feet with an average depth of 5 feet holds approximately 19,200 gallons. Smaller plunge pools (10 × 20 ft) may hold around 7,500–10,000 gallons, while large residential pools (20 × 40 ft) can exceed 30,000 gallons. Above-ground circular pools are often smaller, commonly holding 5,000–15,000 gallons depending on diameter. Knowing your approximate size helps you cross-check the calculator's result and catch any input errors.