How do I find the dimensions of my air filter?
Air filters use two sets of dimensions: actual and nominal. The actual dimensions are the exact height, length, and width measurements. Most filters are sold under nominal dimensions, which are rounded off to the nearest 1" measurement. For example, if your air filter measures 10 ½“ x 20 ¾” x 1¼”, the nominal dimensions will typically be 11” x 21“ x 1”. To find your filter size, we recommend measuring the actual dimensions of your existing filter and choosing the closest match in nominal dimensions.
Filters should fit snugly without having to be forced into place. Forcing in a filter that is too large can cause tearing or buckling and results in a loss of efficiency. If you notice air leakage around the sides after installation, you may use gasket tape around the edges of the filter to create a tighter fit.