Last updated: 2026-06-16

The volume of a swimming pool is its surface area multiplied by its average depth. Once that figure is known, it sets the dose of every chemical the water needs, the cost of filling, and the flow rate required to circulate the water through the filter.

Surface Area by Shape

For a rectangular pool the surface area is length times width. For a round pool it is the area of a circle, set by the diameter:

Multiplying the surface area by the average depth gives the volume:

Average Depth

Most pools slope from a shallow end to a deep end, so a single depth measurement is not enough. The average depth is the mean of the shallow-end and deep-end depths:

A pool measuring 1.0 m at the shallow end and 2.0 m at the deep end has an average depth of 1.5 m. A pool with a constant floor uses that single depth directly.

Worked Example

Consider a round above-ground pool with a diameter of 6 m and a uniform depth of 1.4 m. The radius is 3 m, so the surface area is $\pi \times 3^2 = 28.27\ \text{m}^2$. Multiplied by the depth:

That is about 39,584 litres, or roughly 10,457 US gallons.

Why the Figure Matters

Pool chemicals are dosed per unit of water, so the volume is the basis for every calculation that keeps the water clear and safe. A chlorine dose worked out for the wrong volume either leaves the water under-treated or wastes product. The same volume drives the fill cost and the pump turnover rate. Related estimators include the Concrete Volume Calculator for the pool shell and Fuel Cost Calculator for running costs.