When in doubt, contact your pool service professional to calculate your pool water volume. Have you ever wondered how much water is in your swimming pool? Have you even ever wondered why you need to know the amount of water in your pool? The swimming pool contractors from Seahorse Pools explain that knowing the volume of water in your pool helps you know how long the pool pump needs to be run in order to turn the pool water over at least once daily. Knowing the volume of the pool water also helps you know how many gallons of chemicals to add to the pool water.

How much water is in your swimming pool?

The calculations for the volume of your pool can be determined and provided by a pool service professional who can take the appropriate measurements and determine the gallons of your pool.

How is the volume of water in a swimming pool determined? 

Nearly every aspect of a swimming pools circulation, filtration, and water chemistry, is reliant upon the volume of the pools water in both gallons and its weight in pounds. Here are the formulas that those in the swimming pool industry use to calculate water volume.

  •  Water volume in a pool in gallons: ( Pools Surface area (SA) x Pools Average Depth (AD) ) x 7.48 (Gallons in a cubic ft)  (SA x AD) x 7.48 = gallons
  • Weight of the water in pounds:  Gallons x 8.33 (pounds per gallon)
How can a pool owner determine these dimensions? 

When a pool company designs a pool, the dimensions of the pool, including surface area, perimeter, average depth, and volume, are listed on the construction plans. If you have a copy of the original plans for your pool that is the best place to find the most accurate information. In the event no plans are available, the next method is the next best thing.

Note: Pools come in many shapes. If they were all rectangular the task would be simplified.

For example: 

  • For a rectangular pool, just measure then multiply, the length x width to get the SA (surface area).
  • Then measure the depth of the center of the shallow end and the center of the deep end, add the two numbers together and divide by 2 to get the AD (average depth).
  • However, if the pool is not rectangular you will have to do your best to determine the “average” width and the “average“ length of the pool.
  • If the pool is very irregular you can take the measurements of width, every 2 feet down the length of the pool. Then add all the measurements together and divide by the number of measurements taken to get the “average” width.
  • You would do the same for the pools length as well to get the “average” length.
  • Once you have these just multiply the average length times the average width to get the average “surface area” (SA) of the pool.
  • Then use the previously discussed method to determine the “average depth” and use the formula we discussed.
  • (SA x AD) x 7.48 = gallons of water in the pool.
Area of a circular pool:
  • If you were lucky enough to have a pool that was a perfect circle, you can use an alternate formula.
  • The surface area of a circular pool is 3.14 x the radius2.
  • So just measure the distance across the round pool, divide that by 2 and multiply the number by itself to get the “radius2”. Then multiply that number by 3.14. Then multiply the answer by the average depth. You now have the gallons.

Of course, as stated earlier, these calculations can also be provided by a pool service professional who can take the appropriate measurements and determine the gallons of your pool. Your swimming pool contractor can help you determine the dimensions and water volume. Once you have the facts and figures, write them down and keep them with your pool paperwork for future reference.