First, most home air filters state the dimensions right on the filter frame. So take a look there first, and it would be 3 dimensions separated by "x"s. That is how you'll see sizes organized in our Air Filter Wizard. If you don't see filter measurements on your air filter frame, here is how to measure your home air filters. Whether you have standard filters or "custom air filters, " chances are On Time Air Filters can ship your filter size(s) in 48 hours or less, so you've come to the right place.
An air filter has three dimensions, height, width and depth. To measure your filter, stand the filter on its side with the pleats running horizontally (parallel to the floor). Height is the vertical dimension from the floor to the top of the filter in this orientation, width is across from left to right, and depth is the thickness of the air filter from front to back. You can also determine these sides based on how the air filter is positioned in the system. Typically, the air filter is positioned in the system with the pleats running horizontally.
Filter depths are standardized but a little misleading. For example, a 1” filter is actually about 1/2” wide, while a 2” filter is about 1 1/2” wide. Measure yours and round that up to the nearest whole number. In other words, if the depth of your filter is 5/8”, you need a 1” filter.
Filter height and depth are the most critical measurements. Measure each dimension to the nearest 1/8”. In general, a filter height of 24" corresponds to a true height of 23 and 5/8 to 23 and 7/8 inches.