How to Measure for Filters

How to get the right Air or Furnace Filters

The air or furnace filter is located near the blower or air handler of the unit.  Getting the correct air and furnace filter is important because a poorly fitted filter will allow air and allergens to escape.  Filters should fit as exact as possible in order to function as optimum performance.  Here are the steps to getting the correct filter for your home.

1.  Take the filter out and check the top of the filter for the size.

2.  If a size is not noted on the filter then measurements will need to be taken.

3.  A filter that measures 24 x 24 x1 may have exact measurements of 23 5/8" x 23 5/8" x 13/16". This is the nominal filter size and it is generally rounded up to the nearest whole inch.


Measure exact size of filter length, width, and thickness.  If filter is unavailable, measure opening.  Keep in mind that filters are nominally cut, so when you place your order, exact dimensions will be critical in ensuring the right fit.  Custom filters are non-refundable, so please measure carefully.  Merv 8 and Merv 11 filters are sold by the case, and each filter last approximately 3 months (some time difference may occur).