How the square pool volume calculator works
Side times side gives the surface area. Multiply that by average water depth for cubic feet, then by 7.48 for US gallons.
If one corner is deeper, average the shallow and deep readings before applying them.
The formula
Volume = side x side x average depth
Measure: Side length, average depth.
Worked example
An 18 foot square pool covers 324 square feet. At an average depth of 4.5 feet that is 1,458 cubic feet.
That equals roughly 10,907 gallons, or 41,290 litres.
Tips before you measure
Check both directions before you assume the pool is square. Many are a foot or two out, which is enough to matter.
Measure the inside of the liner at the water line for the truest number.
Square pool volume FAQs
How many gallons is a 15 foot square pool?
At 4 feet deep a 15 foot square pool holds about 6,733 gallons, or roughly 25,490 litres.
What if the sides differ slightly?
Use the rectangular calculator with both measurements. It is more accurate than averaging.
Does depth need to be uniform?
No. Enter a shallow and a deep reading and the calculator averages them.
Other pool shapes
Not quite the right outline? The main pool volume calculator covers all 20 shapes with the same units and formulas.