Door backset is one of the most important measurements to check before purchasing a new door knob, lever, deadbolt, handleset, or replacement latch. Even when the new hardware looks like the correct size, it may not fit properly if its latch is incompatible with the existing backset.
Fortunately, measuring door backset only takes a few seconds. This guide explains what backset means, how to measure it, and what to check before ordering new door hardware.
What Is Door Backset?
Door backset is the horizontal distance from the edge of the door to the center of the main bore hole where the door knob, lever, or deadbolt is installed.
In other words, it determines how far the operating hardware sits from the edge of the door. The latch or deadbolt must extend through the door edge and line up correctly with the center of the bore hole.
Most residential door hardware uses one of two backset measurements:
2⅜-inch backset: Commonly found on residential doors.
2¾-inch backset: Often found on exterior doors, commercial-style applications, and some older or specially prepared doors.
Some older doors may use less common measurements, including a 5-inch backset. These applications generally require specialized replacement hardware or a compatible extended latch.
How to Measure Door Backset
You can measure the backset with the existing hardware installed or after removing the knob, lever, or deadbolt.
Method 1: Measure to the Center of the Hardware
Place the end of a tape measure against the edge of the door. Measure straight across the face of the door to the center of the knob, lever spindle, or deadbolt cylinder.
The measurement will usually be approximately 2⅜ inches or 2¾ inches.
Method 2: Measure the Existing Bore Hole
If the hardware has been removed, measure from the edge of the door to the center of the large circular bore hole.
Do not measure to the near edge or far edge of the hole. The measurement must end at the hole’s center point.
Do Not Include the Latch Faceplate
Begin measuring from the actual edge of the door. Do not begin from the outer edge of the latch faceplate, because the faceplate may be recessed into the door.
Why the Backset Measurement Matters
The latch connects the hardware on the face of the door to the door edge. If the latch length does not match the door’s backset, the spindle, tailpiece, or mounting posts may not line up with the latch mechanism.
An incorrect backset can cause several problems:
The knob or lever may not connect to the latch.
The deadbolt tailpiece may not pass through the correct opening.
The mounting screws may not align.
The latch may bind or fail to retract properly.
The trim may not sit correctly against the door.
Checking the measurement before ordering is especially important when replacing older hardware or purchasing separate lock components.
Adjustable and Fixed-Backset Latches
Many modern residential knobs, levers, and deadbolts include an adjustable latch that can be configured for either a 2⅜-inch or 2¾-inch backset.
However, not every latch is adjustable. Some products use a fixed 2⅜-inch latch, a fixed 2¾-inch latch, or a specialized latch designed for a particular lock series.
Never assume that a replacement latch will work simply because it is made by the same brand. Verify the product series, backset, latch type, faceplate shape, and compatibility information before ordering.
Backset vs. Bore-Hole Size
Backset and bore-hole diameter are separate measurements.
Backset is measured from the edge of the door to the center of the bore hole.
Cross bore refers to the large hole drilled through the face of the door for the lock hardware.
Edge bore refers to the smaller hole drilled through the edge of the door for the latch or deadbolt bolt.
A common residential door preparation uses a 2⅛-inch cross bore and a 1-inch edge bore, but product requirements can vary. Always review the manufacturer’s specifications or installation template before modifying a door.
Check the Latch Faceplate
Backset is not the only latch measurement that matters. The latch must also match the preparation on the edge of the door.
Common latch configurations include:
Square-corner faceplate: A rectangular plate with square corners.
Radius-corner faceplate: A rectangular plate with rounded corners.
Drive-in latch: A round collar that presses directly into the edge bore without a rectangular faceplate.
When replacing existing hardware, matching the current latch style can reduce the amount of door preparation required.
What If the Door Has an Unusual Backset?
Older doors and specialty applications do not always use current standard measurements. If the backset is not 2⅜ inches or 2¾ inches, do not enlarge or redrill the door until you have identified the correct replacement options.
Possible solutions may include an extended-backset latch, replacement hardware designed for older door preparation, or professional modification of the door.
Also inspect the door for decorative molding, glass, or narrow stiles. Large trim plates may not fit if there is limited space between the bore hole and a raised panel or glass opening.
Other Measurements to Check
Before ordering replacement door hardware, record the following information:
Door thickness: Measure from one face of the door to the other.
Cross-bore diameter: Measure the large hole through the face of the door.
Edge-bore diameter: Measure the latch hole through the door edge.
Latch faceplate: Identify whether it is square corner, radius corner, or drive-in.
Door handing: Some levers and handlesets require the correct left-hand or right-hand configuration. Review our door handing guide when the product is handed.
Center-to-center spacing: For handlesets or doors with two bore holes, measure from the center of the upper hole to the center of the lower hole.
Choosing Compatible Door Hardware
Once you know the backset and other door measurements, you can select hardware that matches the existing preparation.
Browse door knobs for passage, privacy, dummy, and keyed-entry applications.
Browse door levers for residential and commercial-style door applications.
Browse deadbolts for exterior door security and replacement projects.
Browse door latches when replacing a worn or incompatible latch component.
You can also view our complete selection of door hardware to compare related products and accessories.
Final Thoughts
Door backset is the distance from the edge of the door to the center of the main hardware bore hole. Most residential doors use either a 2⅜-inch or 2¾-inch backset, but older and specialty doors may use other measurements.
Measure the existing door before ordering, and confirm the backset, bore-hole sizes, door thickness, latch faceplate, and any handing requirements. Taking these measurements in advance makes it much easier to select door hardware that fits and operates properly.
Need help identifying compatible hardware? Contact Factory Direct Hardware with the product brand, model number, door measurements, and photos of the existing installation.