What's the Backset of a Door?
The 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 or deadbolt. In the United States, there are two common backsets for residential door locks:
- 2-3/8 inches
- 2-3/4 inches
Why Are Backsets Important for Door Locks and Latches?
Knowing your door backset lets you find door locks 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 door backset isn't long enough, a spring-loaded latch won't engage fully and may not keep the door closed. The bolt on a lock may not fit into the hole or strike box on the frame and you may not be able to engage the bolt at all.
Dummy knobs and dummy handles don't have latches and don't require a specific backset. 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
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.
Creating Door Preparations for Locksets and Deadbolt Locks
Standard Door Measurements and Handing
If you're shopping for new doors or door hardware, it's helpful to know some of the measurements and understand door handing.
Exterior Door Dimensions
The standard height for an exterior door is 80 inches. Widths can vary widely. Most single doors are 32 or 36 inches wide. Most double doors are 64 or 72 inches wide. You'll see additional variation in widths if the door includes sidelights – panels of glass on one or both sides of the door. The standard exterior door thickness is 1-3/4 inches.
Our exterior door guide will show you what you need to look for when shopping for an exterior door.
Interior Door Dimensions
An interior door is usually 80 inches tall, but widths can vary. The most common are 24, 28 and 30 inches. Most interior doors are 1-3/8 inches thick. The door may be slightly beveled to ease closure into the jamb.
Take a look at our interior door guide to see the available styles and options.
Patio Door Dimensions
Patio doors are constructed of glass and a frame. The standard height is 80 inches. Single door widths can be 30, 32, 34 or 36 inches. Double patio doors are usually 60 or 72 inches wide.
Read our patio door guide to find the right door for your home.
Door Handing
It's good to know the handing or the swing of a door when replacing hardware, particularly if you're installing door levers. Some may work only with one type of swing.
To determine the handing of a door, stand in the doorway with your back against the frame where the hinges are installed. If the door knob or lever is closest to your right arm, the door has a right-hand swing. If the door hardware is closest to your left arm, the door has a left-hand swing.