How to calculate pool volume in liters
A practical method for rectangular, round and variable-depth pools.
What the calculation represents
Pool calculations should use water dimensions and average depth. For a uniformly sloped floor, average the shallow and deep readings before multiplying by surface area.
- Reference formula
liters = ft³ × 28.316846592; US gallons = ft³ × 7.48052- Unit reference
- 1 L = 1,000 cm³ · 1 m³ = 1,000 L · 1 US gal = 231 in³ = 3.785411784 L
A practical workflow
- Measure the water surface and split an irregular pool into rectangles, circles or sections that can be calculated independently.
- Average shallow and deep readings only for a uniform slope; calculate shelves and separate-depth zones on their own.
- For feet, multiply surface area by average depth and 7.48052 to obtain US gallons; retain cubic feet as a cross-check.
- Subtract steps, benches and other physical displacement not already represented in the section model; do not deduct modeled curves a second time, then calibrate with a water-meter reading during a known full fill when practical.
Worked example
A 20 × 10 ft pool averaging 4.5 ft deep contains about 6,732 US gallons, or roughly 25,480 liters, before allowing for steps and freeboard.
Reading the answer correctly
Irregular outlines should be split into simpler sections instead of forced into one rectangle.
On a 20 × 10 ft pool, a 2-inch error in average depth changes the estimate by about 249 US gallons. Multiple depth readings usually matter more than carrying extra decimals.
Elliptical and stadium-shaped pools are different
An elliptical pool uses ellipse area. A common oval pool with straight sides and semicircular ends is a stadium shape: a central rectangle plus one complete circle. Length and width are the total waterline dimensions, with length greater than or equal to width.
At 6 × 3 m with 1.4 m depth, the ellipse holds approximately 19,792 L, while the stadium shape holds about 22,496 L. A single universal “oval pool factor” would mix two different geometries.
The average of shallow and deep readings represents the pool only when the slope is uniform. Benches, steps, and multiple floor levels need separate sections.
Ellipse: area = π × length × width ÷ 4Stadium: area = (length − width) × width + π × (width ÷ 2)²
Checks before relying on the number
- Dimensions follow the waterline rather than coping, deck edge or advertised outside size.
- A round pool calculation squares radius, not full diameter.
- US gallons are not confused with Imperial gallons in equipment or chemical instructions.
- Chemical dosing uses a verified working volume and follows the product label.
Sources and references
These references support the units, method, or limitations explained in this guide.
- NIST — SI units of volume
Official reference for the liter, cubic meter, and metric relationships used in the calculations.
Keep a section sketch and any meter-based calibration factor so filter sizing, refill planning and future dosing use the same defensible volume.
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