how to calculate pool filter square footage


Author: Poolking - Swimming Pool Equipment Manufacturer

When it comes to keeping your swimming pool clean and clear, your pool filter plays a crucial role. The pool filter helps to remove debris, dirt, and other contaminants from pool water, leading to crystal clear water for you to swim in. However, the effectiveness of your pool filter greatly depends on the size and square footage. In this article, we will take you through how to calculate pool filter square footage and ensure that your pool remains clean and clear all year round.

Understanding Pool Filter Square Footage

Pool filter square footage is a measurement of the area of the filter media within the pool filter. The filter media is the part of the filter that catches the debris and other contaminants in the pool water. The area of the filter media determines the amount of water that can flow through it and the amount of debris it can catch before it requires cleaning.

Different pool filter types have differing square footage. The square footage of a pool filter depends more on the size (water volume) of the pool rather than the shape. A larger pool will require more filter surface area compared to a smaller pool.

To understand the square footage of your pool filter, you need to know the volume of your pool. Once you determine your pool's gallons, you will determine the type of filter needed and the required square footage.

Calculating the Pool Square Footage

Now that you know that pool filter square footage is dependent on the volume of your pool let's dive right into how to calculate it. Calculating the pool square footage depends on the type of pool you have since different shapes of pools have different volume formulae. Here's how to determine the square footage for each pool type:

1. Round Pools

For round pools, the formula is simple: radius^2 x pi (3.14) x average depth x 7.5. Measure the distance from the pool radius to the center to determine the radius. For instance; if your pool depth ranges between 4-6 feet, the average depth will be 5 feet.

2. Oval Pools

For oval pools, the formula goes thus: length x width x average depth x 5.9. In this case, measure the widest part of the pool width to determine it.

3. Rectangular Pools

Calculating the square footage of a rectangular pool is as simple as multiplying the length by the width by the average depth by 7.5.

Understanding the Required Filter Size

Once you have determined your pool size and volume, you can select your pool filter size. The size of your pool filter is dependent on the pool's gallons and not the size of the filter device itself.

Filters are rated according to the amount of gallons they can filter. Some common types include diatomaceous earth filters, cartridge filters, and sand filters. The filter will be rated in gallons per minute (GPM), and the volume of the pool water will determine which filter rating you require.

The rule of thumb for filters is that the GPM of your filter should be able to filter the water volume of your pool twice in 8 hours. Therefore, divide the total gallons in your pool by 8 hours and then multiply by 2 to determine the GPM required for your pool.

Maintaining Your Pool Filter

Proper maintenance of your pool filter is critical to ensure that it remains effective. Backwashing or replacing the filter's cartridge/diatomaceous earth or sand at regular intervals is necessary. These intervals depend on factors such as pool usage, surrounding trees or plants, and climate conditions.

You should also check your pool filter at least once a week throughout the swimming season to ensure it's clean and functioning correctly. All pump baskets and pool skimmers should also be cleaned regularly to reduce the load on the pool filter.


Calculating pool filter square footage is essential for maintaining clean and safe pool water. Determining your pool size and volume will help you decide on the correct filter size required to ensure efficient filtering. Ensure that you also maintain your pool filter regularly to achieve optimal water clarity, and always have testing kits to test for sanitizer and pH levels in the pool water; this will help prolong your pool season while providing you with crystal clear water throughout the season.


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