When it comes to air filters, it's important to understand that standard sizes may vary slightly. If you have to force an air filter in or out, it's the wrong size, so standard sizes are usually half an inch smaller than advertised. 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. All filters have two different sizes: a real size and a nominal size.
The actual size is the exact dimensions without rounding, while the nominal size is the rounded dimensions of the filter. It's important to note that air filters, furnace filters, AC filters and air conditioning filters are all the same. So if you need to find household air filter sizes, HVAC filter sizes, furnace filter sizes or air conditioning filter sizes, you're looking at the same thing. To make it easier to find the correct filter size for your oven, use a table as an oven filter size finder.
The actual size is usually on the filter just below the nominal size and is usually labeled as such. When you buy a filter online, the actual size appears at some point in the product list or in the product description. If the filter does not have actual dimensions on the outside of the filter, you can measure it to get the correct dimensions. To ensure that your next filter is the correct size for your system, measure the inside dimensions of the air filter inlet.
If you live in an older house with a non-standard size air return frame, you can use adhesive foam insulation tape to slightly increase the dimensions of your preferred filter or order a custom-sized air filter. For common brands of HVAC systems such as Goodman, Lennox, Trane, Rheem York, Coleman and Carrier, most standard air filter sizes will work. The primary function of an air filter is to protect your HVAC equipment from damage that can be caused by dust and debris accumulation on coils. When searching by brand like Lennox or Carrier to find a Carrier oven filter size by model number, use a Carrier filter size search from a table or with a Lennox size search.
Filters are measured by nominal size, which is a rounded number that varies by brand; many filters have part numbers of each brand they are compatible with. Whole house AC filters with a size of approximately 3 to 6 inches wide can have a lifespan of 6 to 12 months depending on environmental conditions. Actual size refers to exact measurements of your air filter and its dimensions when measuring length, width and depth (thickness). Most white pleated air filters are inherently similar within each efficiency level, varying slightly between brands.
If you have to clog an air filter to install it, try a different brand of oven filter or a custom-sized air filter with a slightly smaller actual size. If you're looking for a retailer near you that sells custom-sized air filters, you might be struggling to get lucky.