The furnace filter “size issue”

Just the thought of replacing a furnace filter can be headache-inducing, but we’re here to ease your pain. This article offers a quick snapshot of how to find the right size filter for your furnace the next time it needs replacing.

Scenario One: Your Current Filter Includes Dimensions

If you have an old filter from your furnace on which the dimensions are printed, then ascertaining size is a non-issue. You can use these provided dimensions to locate and order  new filters in the same size. Keep in mind, though, that those dimensions are not the actual dimensions of the opening in your furnace where the filter is installed. These dimensions are known as “nominal dimensions,” which means that they are rounded up to the nearest inch measurement. The dimensions of the opening are known as “actual dimensions.” Most companies that sell furnace filters will reflect the nominal dimensions, so if the actual size of your opening is 15 ½” by 24 1/2”, the nominal dimensions of the filter you want is 16 by 25.

Scenario Two: Your Current Filter Lacks Dimensions

If you can't ascertain your furnace filter’s nominal dimensions, there is no need to panic. You can simply measure the opening for filter and round up to the nearest inch. For example, if the actual opening is 14 by 19 ½, the nominal dimensions you want to specify are 14 by 20.

When it comes to furnace filters, size may be an issue. As we’ve shown here in this quick guide, however, the size issue can be easily resolved.