Swimming Pool Volume Calculator

Calculate how many gallons your swimming pool holds based on shape and dimensions.

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Enter your values and click Calculate

Knowing your pool's volume in gallons is essential for correct chemical dosing, salt system calibration, pump sizing, and water cost estimation. Adding too little or too much chlorine, pH adjuster, or algaecide without knowing your pool's volume leads to ineffective treatment or dangerous chemical levels. This calculator supports three common pool shapes: rectangular (standard in-ground), oval (common for above-ground pools), and circular (round above-ground pools). Enter your pool's length, width (or diameter for circular), and average depth. For pools with a shallow end and a deep end, use the average depth ((shallow depth + deep depth) ÷ 2). Results are shown in both US gallons and liters.

How It Works

Volume is calculated differently by shape. Rectangular: gallons = length × width × avg depth × 7.48. The factor 7.48 is the number of US gallons in one cubic foot (7.48052 exactly). Oval: gallons = length × width × avg depth × 5.9. The factor 5.9 is an industry standard that accounts for the elliptical shape (it equals 7.48 × π/4 × average-width correction used in the pool industry). Circular: gallons = π × (diameter/2)² × avg depth × 7.48, which calculates the volume of a cylinder. For pools with a sloped bottom (shallow to deep end), use the true average depth: (shallow depth + deep depth) ÷ 2. For pools with a flat shallow area, a slope, and a deep area, a more precise calculation involves treating each section separately. Liters = gallons × 3.78541.

Examples

Standard In-Ground Pool
A 30×15 ft rectangular pool with an average depth of 5 ft.
Result: About 16,807 gallons (63,596 liters).
Round Above-Ground Pool
A 24 ft diameter circular above-ground pool, 4 ft deep.
Result: About 13,594 gallons (51,459 liters).
Oval Above-Ground Pool
An 18×12 ft oval pool, 4 ft deep.
Result: About 5,097 gallons (19,296 liters).

Frequently Asked Questions

Why do I need to know my pool's volume?
Pool chemical dosing instructions are expressed per 10,000 gallons. Without knowing your pool's volume, you cannot accurately dose chlorine, pH adjusters, alkalinity increasers, algaecide, or stabilizer. Underdosing leads to algae, cloudy water, and bacterial contamination. Overdosing creates irritating or dangerous chemical concentrations and wastes money. Salt chlorine generators require the pool volume to be programmed for correct output calibration. Pump and filter sizing is also based on the volume of water that needs to cycle through in a given period.
How do I determine my average depth?
For a pool with a uniform depth, average depth equals actual depth. For a pool with a shallow end and deep end, average depth = (shallow end depth + deep end depth) ÷ 2. For example, a pool that's 3 ft at the shallow end and 7 ft at the deep end has an average depth of 5 ft. For a pool with a flat shallow section, a transition slope, and a flat deep section, a more precise approach is to calculate each section's volume separately and add them together.
What is the oval pool formula based on?
An oval pool approximates an ellipse. The exact formula for an ellipse's area is π × (length/2) × (width/2), which equals approximately 0.7854 × length × width. Multiplying by depth and 7.48 gives volume in gallons. The industry commonly uses a factor of 5.9 instead of the mathematically exact 5.87 (7.48 × 0.7854), which is a conventional approximation. The result is slightly conservative — actual volume may be marginally higher.
How often should I test my pool's chemistry?
For residential pools in regular use, test pH and free chlorine at least twice per week. Test total alkalinity, calcium hardness, and stabilizer (cyanuric acid) once a week when first balancing the water, then monthly once stable. After heavy rain, a large number of swimmers, or chemical additions, test more frequently. Maintain pH between 7.4 and 7.6 and free chlorine between 1 and 3 ppm for safe, clear water. Proper chemistry reduces the need for shock treatments and extends the life of pool equipment and surfaces.

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