What's the Backset of a Door?
A door backset is the distance from the edge of the door to the center of the 2-1/8-inch bore hole for the door knob, lever, handleset or deadbolt. In the United States, there are two common backsets for residential door locks:
- 2-3/8 inches
- 2-3/4 inches
Your backset measurement should match the latch or bolt size of your door hardware.
Why Are Backsets Important for Door Locks and Latches?
Knowing your door backset lets you find door knobs, handles and deadbolt locks that fit your door. If the backset on a door doesn't match that of your door hardware, the latch or bolt won't work correctly:
- If the door backset is too long for a lockset or deadbolt lock, the latch or bolt may not extend far enough into the door frame to fully secure the door.
- If the handle or door knob backset isn't long enough, the spring-loaded latch on the knob or handle won't engage fully and may not keep the door closed. The bolt on the lock may not fit fully into the hole or strike box on the frame and you may not be able to engage the bolt at all.
Since matching the door backset to the hardware is a must for a secure door, many types of door hardware have an adjustable backset, allowing you to easily fit them to your existing doors.
Dummy knobs and dummy handles don't have latches and don't require specific backsets. They simply mount on the surface of a door. You can place them anywhere on the door but matching them to the height and backset of the hardware on your other doors looks best.
What's the Difference Between a Residential and Commercial Door Backset?
Residential and commercial doors often have different backsets. While residential doors may have a backset of either 2-3/8 inches or 2-3/4 inches, a commercial door will usually have a 2-3/4-inch backset.
Door Preparation for Knobs, Handles and Deadbolt Locks
The door preparation or door prep is the set of holes drilled or bored into the door for the mechanism of a latch or lock. Most door hardware mechanisms fit into the door prep shown here.
If you’re replacing existing hardware, then your door prep will most likely be correct for most locks. Once you determine the backset, you're ready to purchase the hardware. Installation should be relatively simple.
If you're installing locks in new doors that don’t have a door prep, the basic instructions are below. See our articles on installing a knob or lever and installing a deadbolt for detailed steps. Check your door hardware for any measurements or steps specific to your model.
Learn how to install an interior door and install an exterior door with our how-to guides. Don’t have time to do it yourself? We can install your doors. Get started.
Step 1: Bore a Hole for the Mechanism
Use a drill and hole saw to bore a 2-1/8-inch hole through the door. The center of this hole should be 2-3/8 inches or 2-3/4 inches back from the edge of the door. This is the backset measurement.
Using a door lock kit is a simple way to prep a door for hardware. These kits usually include the drill accessories you need and a jig to make the work quicker.
Step 2: Bore a Hole for the Latch or Bolt
Use a 1-inch hole saw or spade bit to bore a hole in the edge of the door at the centerline of the 2-1/8-inch hole. The latch for your knob or handle or the bolt for your deadbolt lock fits through this hole. Check your measurements carefully before you cut the hole to ensure alignment and smooth operation of the hardware.
Step 3: Cut a Mortise for the Latch Faceplate
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 sits in this recess or mortise.
If you’re using an installation kit with a mortise template, you can simply attach the included router bit to your drill and cut the mortise.
When it’s time to buy new knobs, handles or locks, take a look at our door hardware guide. If you need new hardware but don’t have time to install it yourself, we can help. You can purchase some door hardware and accessible handles and locks with installation. Just add installation to your cart when you check out.
Shopping for Doors and Hardware
If you're purchasing new doors or door hardware, it's helpful to know some of the measurements and understand door handing. See our exterior door guide and our interior door guide to learn about door sizes, handing and other factors to consider.