Formulas and examples
How to calculate pool volume
Choose the formula for the internal water surface, then account for depth and submerged features.
Calculate area at the waterline, multiply by average depth, then convert cubic metres to litres.
Rectangle or square
For a flat floor, use the direct formula. Example: 8 m × 4 m × 1.5 m = 48 m³, or about 48,000 litres.
Sloping floor
For a regular slope, use the arithmetic mean of the depths. Example: (1.1 m + 1.9 m) ÷ 2 = 1.5 m. An 8 × 4 m pool then holds about 48 m³.
Round or oval pool
For a circle, multiply π by the radius squared and average depth. For an ellipse-like oval, multiply π by both semi-axes and average depth.
- Oval: π × half-length × half-width × average depth.
- Measure at the waterline.
- Check what any simplified commercial coefficient represents.
L-shaped or free-form pool
Split an L into two non-overlapping rectangles. For a free form, divide the pool into slices, estimate each width and depth, and add their volumes.
The more the width and floor vary, the more useful a point-based outline and slice calculation become.
From gross to net volume
Deduct the solid volumes of steps, benches and sun shelves. Split an irregular staircase into individual steps. Round only to a precision supported by your measurements.
FAQ
How do I convert m³ to litres?
Multiply cubic metres by 1,000.
Which coefficient should I use for an oval pool?
Use the ellipse formula with π and both semi-axes. Simplified coefficients only provide an approximation.
Can an L-shaped pool be calculated?
Yes. Divide it into non-overlapping rectangles and add their volumes.
Sources and limitations
Calculate area at the waterline, multiply by average depth, then convert cubic metres to litres.