What is a Standard Home Air Filter and How to Find the Right Size

Air filters are essential for keeping your home's air clean and healthy. But, how do you know which size air filter to buy? Each unit has a specific size filter that allows it to operate correctly and efficiently. Most air conditioning and HVAC units use standard-size filters, but some require the purchase and installation of a custom-sized air filter. The filters are labeled with three-part dimensions.

The first number is its length, the second is its width, and the third is its depth or thickness. To find the right size air filter for your home, you'll need to measure the length and width of the existing filter. The easiest way to identify the size of the AC filter is to remove the existing filter from its slot and examine the filter frame. Typically, the filter size is printed along the edge of the filter frame. Note that the size shown in bold type on the filter frame is the nominal size of the filter, which is likely to differ from its actual size.

If the actual dimensions do not appear in small print on the filter frame, we recommend measuring the filter for double checking. If you use a room air purifier and need to replace the filter, it's important to find the correct size replacement HEPA filter. Installing several 1-in-a-slot air filters, for example, can cause costly damage to your air conditioning unit, as residential ovens are not equipped to handle this level of airflow restriction. If the filter is too small, it will loosen and some of the air (and dirt) will not pass through the air filter. Lennox has a MERV 16 filter option as an offer on the Lennox Pureair system, which is among the highest-efficiency residential filters available and Lennox also recommends it as an upgrade to specific Carrier, Trion Air Bear and Honeywell systems. Of course, this sounds easy when you hear the term “standard air filter size”; you might think that if your air filter is standard, it will be easy to find it when you arrive at the store. The image of this 12 x 12 x 1 inch air filter has the nominal size, which is the size that air filters are usually sold for. You also don't want to place an air filter 1 in a slot 2 because the air takes the path of least resistance and will flow around the filter instead of through it if it's not the right size.

The list of location HEPA filters for sale usually includes compatible models in the description or in bullet points, so be sure to check for compatibility to ensure you buy the right HEPA filter for your air purifier. If you live in an older home with a non-standard size air return frame, you can use a foam weatherstrip tape to slightly increase the dimensions of your preferred filter or order a custom-sized air filter. This rounded measurement is called the nominal size and is used to match the correct filter to the air cleaner slot of your accessory. How often you change your home's air filters depends on their type and environmental conditions such as smoke, dust or construction. If you have a system that uses a whole-house filter, you may have a choice from MERV 8 to MERV 16 depending on your HVAC system if you have a system that has an option of a highly efficient MERV 15 filter such as Bryan and Carrier offer germicidal air purifiers. Using a properly sized air filter for your HVAC unit is essential to keep your system running smoothly and reap all its benefits. You can usually find out what size your AC unit needs by looking at its existing filter frame.