How Do I Know My Pool Size?

Important: Be sure to use all measurements in Feet, not inches or metric

Knowing your pool size is very important. Traditionally, it helps you know what amount of chemicals you need to keep your pool sanitized and clean. For saltwater pools, you need to know your pool size to determine what model saltwater chlorine generator you need. It just takes some basic math in most cases, though finding your pool capacity can be difficult if the pool has a unique shape or if the slope of the pool floor is uneven.

Measure Longest and Widest Pool Dimensions

Measure the overall length and width of pool. This will give the overall surface area of the pool.

Determine Pool Shape
Choose from the following formulas depending on whether your pool is rectangle, round or oval. For lagoon, kidney, or other freeform pools, you can often get a close approximation by choosing the oval formula.


Length x Width x Average depth x 7.5 = Volume in gallons

Example: 15ft x 30ft x 5.5ft x 7.5 = 18,562 gallons


Since it is a round pool you do not need length and width, you will just need the diameter of the pool.

Diameter x Diameter x Average depth x 5.9 = Volume in gallons

Example: 30ft x 30ft x 5.5ft x 5.9 = 29,205 gallons


Length x Width x Average depth x 6.7 = Volume in gallons

Example: 15ft x 30ft x 5.5ft x 6.7 = 16,582 gallons

Determining Average Depth

Most people don't happen to know what their pool's average depth is. These formulas will help you calculate what that might be.

You will use this formula if your pool has a generally even slope across the pool:

(Deep end (in feet) + shallow end (in feet)) / 2 = _____

For example:

(8 ft Deep end + 3ft shallow end) / 2 = 5.5 ft Average Depth

If your pool has a longer deep end, or a "hopper", use the above instructions to find the average depth of the sloped area. Next estimate what proportion of the pool is sloped, and what proportion is the deep end. Then  use the following formula:

(Sloped Area's Average Depth * X% of the pool this area makes up) + (Depth of Deep End * Y% of the pool this area makes up) = _____

Example with the previous dimensions if the slope makes up 2/3 of the pool, and the deep end's "hopper is about 1/3:

(5.5 ft Average Depth of Sloped Area * 66.7%) + (8 ft Deep End * 33.3%)

After determining your pool size, you can then choose the perfect size system for your pool. Most customers choose a salt water chlorinator 1.5 or 2 times the capacity of the pool. Bigger is always better when choosing a system because it allows your salt cell to work less hard to provide the same amount of chlorine smaller system would. Also, it is more powerful and increases life on your cell. Click on the link below to check out our top-rated systems.

Choose your Saltwater Pool System
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