Swimming Pool Volume Calculator

For a rectangular pool, multiply length × width × average depth to get cubic metres, then multiply by 1,000 for litres. Circular pools use π × r² × average depth, where r is half the diameter. Oval pools are treated as ellipses: π × a × b × depth, with a and b as the semi-axes (length ÷ 2 and width ÷ 2). Irregular pools should be split into those simpler shapes and added together. The calculator on this page applies those formulas for you.

There are exactly 1,000 litres in a cubic metre. A cubic metre is a cube one metre on each side, so it holds 1,000 litres of water. That is why a pool that measures 48 m³ holds 48,000 litres.

Pool volume is commonly quoted in litres, cubic metres, US gallons or imperial gallons. Chemical dosing charts in Europe, Australia and much of the rest of the world use litres or cubic metres. US equipment and many sanitiser labels use US gallons. Imperial gallons are still used in some older UK references. This calculator reports all four so you can match the unit on your product label.

Divide the outline into rectangles, circles and ovals that together cover the water surface. Measure each section, calculate its volume, then add the results. A kidney shape is often two overlapping ovals; a pool with a shallow play area is usually a rectangle plus a smaller rectangle or circle. The irregular mode on this calculator lets you add those sections and sums them automatically.

If the floor is level, one depth reading is enough. If it slopes, measure the shallow-end depth and the deep-end depth and average them: (shallow + deep) ÷ 2. For floors with more than one slope, take several depth readings along the centreline and average those. Steps, benches and beach entries add extra water — include them as additional shallow sections if you need a tighter figure.

The arithmetic is exact; the limiting factor is the measurements you enter. Careful length, width and average-depth readings typically put you within a few percent — close enough for chemical dosing, filling and heating estimates. Freeform edges, Roman steps and vanishing edges add a little extra volume that you can capture by adding sections. Always round up slightly if you are buying sanitiser, so you dose for a full pool rather than an underestimate.