Pool volume calculator
How many gallons is your pool?
Measure three things with a tape measure - length, width, and depth. Enter them below and you'll get your volume in gallons and litres, plus the ionizer size that fits.
Your pool holds
Enter your measurements to see the volume.
Recommended for this pool
Shop this sizeHow to calculate pool volume by hand
Every formula below is area × average depth. The only thing that changes between pool shapes is how you work out the area.
Rectangular or square pools
Length × Width × Average Depth × 7.48 = gallons
The simplest case. Multiply the three measurements, then convert cubic feet to gallons.
Round pools
Diameter × Diameter × 0.785 × Avg Depth × 7.48
0.785 is π ÷ 4 — it converts the square around the pool into the circle inside it.
Oval pools
Length × Width × 0.89 × Avg Depth × 7.48
Most oval pools are a rectangle with rounded ends, so they hold roughly 89% of their bounding rectangle.
Kidney & freeform pools
(Width A + Width B) × Length × 0.45 × Avg Depth × 7.48
Measure the width at the two widest points. The 0.45 factor accounts for the curve.
Average depth
(Shallow Depth + Deep Depth) ÷ 2
If your pool is one depth throughout, that depth is your average. Measure water depth, not wall height.
Working in metres
Length × Width × Avg Depth × 1000 = litres
Metres give you cubic metres directly, and one cubic metre is exactly 1,000 litres.
Two things people get wrong. Measure the water depth, not the wall height — most pools run 6–12 inches below the top. And if your deep end is a steep hopper rather than a gradual slope, averaging the two depths will overstate your volume by roughly 10%. When you're between two ionizer sizes, size up.
