When it comes to air filters, there are two main sizes to consider: the actual size and the nominal size. The actual size is the exact size of an air filter, which you can measure with a measuring tape. This size is usually ¼ to ½ inch smaller than its nominal size. The nominal size is a manufacturer's estimate, which is usually shown on the side of the filter.
This number is rounded for consistency and to avoid confusion for buyers. For air filters 1 and 2, the nominal size does not include the notch, while the actual size does include the recess. For whole-house filters, the nominal size is the rounded size and the actual size is only the unrounded one. Whole house filters typically go to an air controller, which is usually located next to the HVAC system itself.
The easiest way to identify the filter size of your air conditioner is to remove the existing filter from its slot and examine the filter frame. But if your system needs custom-sized air filters, keep in mind that custom sizes ranging from 8 x 24 x 1 to 25 x 30 x 1 are available. It's important to understand that all filters don't need to fit a “tight seal”, but you should be able to easily install and uninstall them effortlessly. Improperly sized air filters can put excessive strain on your HVAC system, damage it, and increase your energy bills.
To ensure you find the perfect size for your home, it's best to consult with a HVAC technician who can evaluate your specific unit and determine what type of filter your oven can handle and what is best for your system. There are two main types of air filters: disposable and reusable. Disposable filters are made of paper or fiberglass and are designed to be replaced every few months. Reusable filters are made of metal or plastic mesh and can be washed and reused multiple times before needing to be replaced. However, these filters can sometimes restrict airflow, which can lead to air and system quality problems.