Air filter guides
Short, plain-English guides to finding, choosing, and changing your furnace or AC filter.
How to find your air filter sizeRead the label, measure the old filter, or measure the slot.Nominal vs. actual air filter sizeWhy a 16x25x1 filter isn't really 16 by 25 by 1.MERV 8 vs. 11 vs. 13: which should you buy?A plain-English way to pick a filtration level.How often should you change your air filter?A simple schedule, and when to change it sooner.Common air filter sizesA reference table of common 1-inch sizes, 10x20 to 25x25.