Furnace filters come in two sizes; nominal size and actual size. For instance, your filter might measure 9-1/2X23-1/2x1, but the nominal size would be 10X24X1.

To figure out the proper size, it is best to take the dimensions of your current filter and round the numbers up to the nearest numerical size. For example: Round 11-3/4 up to 12.

This can get confusing, so don't hesitate to call us at 1-877-476-8422, or use the live chat feature and let us quickly walk you through to the proper measurement.

If you find that your furnace filter is not one of our standard size filters, we do make custom air filters according to our customer's exact specifications.