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Determine the Backset of Your Door

Learn how to measure your door's backset before replacing an existing lock or latch to ensure you get the right fit for your new hardware.


Door backset.

The backset is the distance from the edge of the door to the center of the 2-1/8-inch bore hole. In the United States, there are two common backsets for residential door locks: 2 3/8 inches and 2 3/4 inches. Pack your locks with a 2-3/8-inch or 2-3/4-inch latch, depending on which backset you specify. Dummy sets have no latch and are surface-mounted so you can install a dummy set wherever you choose on the door.

Door Preparation

Door prep.


The door prep is a set of drilled holes in the door, where the latch will fit in. If you’re replacing existing locks, then your door preps will most likely be correct for most locks. Just determine the backset, and you're ready to buy or order. If you're installing locks in new doors that don’t have a door prep, you can follow the instructions below.

Passage, privacy, key-in-knob, or lever, and deadbolt locks

Fit into the door prep shown above. Bore a 2-1/8-inch hole through the door. The center of this hole should be located 2 3/8 inches or 2 3/4 inches back from the edge of the door. (This is the backset dimension.) Bore a 1-inch hole in the edge of the door located on the centerline of the 2-1/8-inch hole. The latch will fit into the 1-inch hole. Chisel out a 1-inch-by-2-1/4-inch rectangle on the edge of the door, 1/8 of an inch deep. The latch faceplate will sit in this recession.

Dummy Sets

Require no door prep. Dummy handles are surface-mounted and may be located anywhere on the door you choose, but they’re usually located to match the appearance of nearby operating locks.

Standard Exterior Doors

The standard size for an exterior door is 80 inches (6 feet, 8 inches) by 36 inches (3 feet). Stock exterior doors are also commonly available in 30-inch and 32-inch widths. The standard door thickness is 1 ¾ inches. Some door manufacturers carry stock doors in 7-foot and 8-foot heights and door widths from 24 inches to 42 inches.

Patio Doors

Patio doors are constructed of glass with a frame. The standard size is 6 feet, 8 inches tall and 6 feet wide. However, patio doors are routinely available in 6-foot, 11-inch and 8-foot heights.

Standard Interior Doors

  • Door parameters: A standard, interior, hollow-core door is classified as a measurement. The most common residential bedroom doors are a 2 feet, 6 inches by 6 feet, 8 inches. Measure width first and then height.
  • Handing: There are two methods of handing or door swing. The first method, or the residential method, is to go to the side of the door where you can see the hinges, when the door is closed. If you can't see the hinges, you're on the wrong side. If you can see the hinges, make the call. The door in the example is a 2-foot-6-inch-by-6-foot-8-inch left.
  • The second method, or the commercial method, is to open the door, back yourself up to the hinge jamb and swing your right arm the way the door swings. So this would be a 2-foot-6-inch-by-6-foot-8-inch right, just the opposite of what we described as residential. 
  • Door Thickness: Most standard interior doors are 1 3/8 inches thick, and the door is slightly beveled to make the closure into the jamb. Buy the correct door hardware for the application so the door handles for passage or privacy have the correct back set and bore.