Pool Volume Calculator (Gallons & Litres)
Calculate how many gallons or litres a pool, hot tub or aquarium holds — rectangular, round or oval, with shallow and deep ends.
How to use
- 1Choose the shape and enter the dimensions in feet (inches for small tanks: enter decimals, e.g. 2.5 ft).
- 2For sloped pools, enter the shallow and deep end depths.
How it's calculated
Average depth = (shallow + deep) ÷ 2. Rectangle: L × W × depth. Round: π × r² × depth. Oval: π × (L ÷ 2) × (W ÷ 2) × depth. Gallons = ft³ × 7.48; litres = ft³ × 28.32.
Frequently asked questions
Why do I need my pool's volume?
Chemical doses, pump sizing and heating costs all depend on the number of gallons.
How full should the pool be?
Usually to the middle of the skimmer opening — measure depth to that water line, not the top of the wall.
How many fish can my aquarium hold?
A cautious rule of thumb is about 1 inch of adult fish per gallon for small fish — less for large or messy species.