Pool Volume
Calculator

For rectangular pools it's simply length times width times average depth. For pools with a shallow and deep end, the calculator averages the two depths since the sloped bottom forms a shape whose volume is well approximated by that average across the full length.

Chlorine, pH adjusters, and algaecide are all dosed based on parts per million relative to total water volume, so an inaccurate volume estimate leads directly to over- or under-treating the water, causing either irritation from excess chemicals or algae growth from too little.

It uses the circle or ellipse area formula (radius squared times pi for round pools) multiplied by the water depth, which is usually more uniform in above-ground pools than in-ground pools with sloped floors.

Use actual water depth, not the wall height, since pools are typically filled to a level a few inches below the top edge for splash-out room, and that gap can meaningfully change the volume for larger pools if ignored.

Manufacturer capacity figures often assume the pool is filled completely to the rim, while real-world operating levels sit a bit lower, and irregular pool liner shapes are rarely perfect geometric solids, so a 5-10% difference between calculated and stated volume is normal.