Measuring correctly for replacement vent covers is very important, but easy. Follow these simple directions and order accordingly:

• First, remove the existing old vent cover completely to expose the “Duct Opening”.
• Next, measure the width of the duct opening. In the diagram below, the width is represented by the “A” notation. Typically, this measurement will be the largest of the 2 measurements. Most duct openings should be whole inch increments and not partial inches. Minor rounding up or down may need to take place.
• Next, measure the height, or depth of the duct opening. In the diagram below, the height is represented by the “B” notation. Typically, this measurement will be the smaller of the 2 measurements. Most duct openings should be whole inch increments and not partial inches. Minor rounding up or down may need to take place.
• Now that you have both measurements, you have what you need to purchase the correct vent cover size. For instance, if your floor duct opening was 10" wide by 4" tall, you'd order a 10x4 vent cover. If your wall or ceiling duct opening was 10" by 6", you'd order a 10x6 vent cover.
• Please note that the interior portion of the new vent cover, or the part that inserts into the duct opening, will be about 3/8" smaller than the duct opening. This will ensure that the vent cover fits properly, and you have some room to square up the vent.
• Also, please note that the overall dimension, or finished dimension of a vent cover, will always be larger than the duct opening by 1-1/2" to 2-1/2", just depending on which vent cover you purchase. This flange that is larger than the duct opening fits flush on the floor, wall, or ceiling, so please make sure you don't have baseboard or crown molding that will interfere.
• If your duct opening is within 1/4" of an even inch increment, you should be fine with ordering a standard size vent cover. However, if your duct opening is more than a quarter inch from a whole inch measurement, 11-1/2" or 4-1/2" for instance, you'll need to request a custom vent cover quote request which can be found here.
  Custom Piece Request