Use the calculator below to determine the open area of your perforated grille in both square inches and as a percentage of the overall grille area.Select Grille Type
Second, enter the overall grille height and length. See illustration for reference.
Then enter the dimensions for the hole opening, which MUST be smaller than the overall grille dimensions you entered above. If you don't know the hole opening size, use the same dimensions as for the overall grille.