Why are there different size air filters?Updated a month ago
Just when you thought air filters weren't confusing enough, it turns out each filter actually has two sizes! "Actual" and "nominal" sizes have entered the chat.
Actual sizes are the exact dimensions of the filter (i.e. if you were to measure it with a tape measure), while nominal sizes are rounded-UP filter dimensions.
Nominal sizes were "created" because they are easier to communicate and market (hence why they are printed directly on the filter frame). Also, that extra sizing buffer from rounding-up gives your fingers some wiggle room when you have to install and replace the filter.