What Size Do Air Filters Come In?

The size of an air filter is usually slightly smaller than the nominal size. Filters are labeled with three-part dimensions, which include the length, width, and depth or thickness. The most popular 1-inch air filters are typically used in air conditioners, ovens, HVACs, and Atomic Filters. We also offer custom-sized filters for those who need a specific size.

When it comes to MERV ratings, you can find more information on our air filter information page. Filters are generally listed by nominal size, which is a rounded number based on the actual dimensions of the filter. The actual size of the filter is known as the actual size. Generally, 1-inch pleated air conditioner filters should be changed every 2 to 3 months depending on use.

If you live in a smoky or dusty environment or have pets, you may need to change your filter more frequently. Whole house air conditioning filters that are 3 to 6 inches wide can last up to 6 to 12 months depending on environmental conditions. If you need to replace an electronic air filter in your oven and require a 5″ × 13″ × 20″ filter, you can find the actual size chart below. The easiest way to identify the size of an air conditioning filter is to remove the existing filter from its slot and examine the filter frame. Usually, the filter size is printed along the edge of the filter frame. Note that the size that appears in bold 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 to check. In this case, you'll need to round down to the nearest whole number to determine the nominal size of your air filter. The actual size of the air filter must be between 0.25 and 0.5 smaller than the slot or frame itself. The slots in the HVAC unit are usually located near the bottom of the air controller. It's best to have a little wiggle room in the slot of the HVAC unit so you can easily slide the filter in and out without it bending or breaking. If you have to clog the air filter to install it, try a different oven filter or a custom-sized air filter with a slightly smaller actual size.

Central air return ventilation grilles are usually found on the hallway ceiling or on the hallway wall of your house. If the return ventilation grille is on the roof, you can opt for a filter that has a slightly larger actual size so that it doesn't fall on you when you open it. When buying a custom-sized air filter, it's important to remember the difference between nominal and actual sizes. Once you've determined the exact dimensions that best suit your needs, order a filter with those exact fraction or decimal measurements. Otherwise, you may get a different actual size than expected. Most large retailers such as Walmart, Target and Home Depot sell air filters with different varieties of options and brands to choose from.

Of course, this sounds easy when you hear “standard air filter size”; however, improperly sized air filters can place excessive strain on your HVAC system and damage it while increasing your energy bills. Aerosolized ions are effective in reducing bacteria, viruses, odors and other contaminants that exist in your home's air. Please note that many filters have similar model numbers; check their actual sizes (actual dimensions measured by the filter) to make sure you have chosen correctly.