There are two formulas you can use to determine the volume of your pool.

The first formula is for a round pool and it is as follows:
Diameter x Diameter x Average Depth x 5.9

Example: a 24′ round pool that was 4 ft. deep would look like this:
24 x 24 x 4 x 5.9 = 13,600 gallons (rounded up)

The second formula is for a rectangular pool:
Length x Width X Average Depth x 7.5

Example: a 20′ x 40′ pool that went from 3′ to 8′ in depth would look like this:
20 x 40 x 5.5 x 7.5 = 33,000