How do I find my A/C Filters or Furnace Filter dimensions?

Every brand of filter has a different exact size.  Most a/c filters and furnace filters have two sizes: Standard and Actual.  If your a/c filter or furnace filter actually measures 15-½ x 19-½ x ¾ then the standard size would be 16x20x1.

When determining the size of your a/c filter or furnace filter, it is best to measure your existing filter. 

You do not want your a/c filter or furnace filter to fit too tight, having to force it into place could damage the filter.  If the filter is too small, it can get sucked up into the return and will not filter the air properly.