Calculating Pool Water Volume and Make-Up Water

The volume of a rectangular pool can be calculated using the following formula:

If the pool floor slopes uniformly from end to end, the average depth can be found by adding the deepest and shallowest depth measurements and dividing the results by two. If the pool's dimensions are in feet, the volume will be in cubic feet. One cubic foot of water equals 7.5 gallons.

Example: The water volume of a pool 60 ft. long, 30 ft. wide and that slopes in depth from 3 ft. to 10 ft. is as follows:

30 x 60 x ((10 + 3)/2) = 11,700 cubic ft. of water

11,700 x 7.5 = 87,750 gallons

Calculating Make-Up Water:
It is helpful to be able to calculate the amount of make-up water that needs to be added to make up for water lose through filter backwashing, splash-out, evaporation or leaks. To do so, determine the number of inches of water depth required to fill the pool and your pool's surface area (length x width) and supplement them into the following formula:

Inches of Water x Pool Surface Area (sq. ft.) x .625 = Gallons of Water