The Half-Inch Difference That Derails a Hardware Schedule
This article explains the two most common latch backset dimensions on cylindrical locksets -- 2-3/4 inch and 2-3/8 inch -- what each one means, where each belongs, and why ordering the wrong one creates a problem you will not catch until the door is already hung. It is written for commercial subcontractors reading a hardware schedule, facility maintenance teams ordering a replacement, and architects verifying a spec before it ships.
What Is a Latch Backset?
The backset is the horizontal distance measured from the edge face of the door to the centerline of the cross bore -- the large hole drilled through the face of the door where the lockset body seats. On a cylindrical (bored) lockset, this dimension determines where the lever, knob, or cylinder will land relative to the door edge, and where the latchbolt projects to engage the strike on the frame.
Get the backset right and the latch hits the strike cleanly. Get it wrong and the bolt misses the pocket, the rose plate overhangs the door edge, or the trim crowds the frame stop -- none of which is fixable without redrilling the door.
The Two Standard Backsets
2-3/4 Inch -- The Commercial Default
The 2-3/4 inch backset (approximately 70 mm) is the standard dimension for commercial cylindrical locksets. Most hollow metal doors, commercial wood doors, and steel frames ship prepared for this backset. If a hardware schedule lists a cylindrical lockset with no backset called out, assume 2-3/4 inch.
- Standard on the vast majority of commercial-grade cylindrical lever locks
- Keeps the lever centerline clear of the frame stop and door edge reinforcement
- Required by most hollow metal door prep standards (ANSI A115 series)
- Used across school classroom locks, office entry functions, healthcare corridor hardware, and industrial facility doors
- Accentra (formerly Yale), Corbin Russwin, Hager, PDQ, and Sargent cylindrical lines all default to 2-3/4 inch on commercial series
2-3/8 Inch -- Lighter Doors and Retrofit Applications
The 2-3/8 inch backset (approximately 60 mm) places the lever centerline closer to the door edge. It originated as the residential standard and remains common on lighter interior wood doors -- particularly those with narrower stiles or pre-bored residential-scale doors.
- Most common on pre-hung wood doors in residential and light commercial construction
- Found in older school and apartment buildings where doors were originally prepared for residential-grade hardware
- Occasionally specified on narrow-stile applications where a 2-3/4 inch backset would crowd the edge
- Many commercial cylindrical locksets ship with an adjustable latch that covers both 2-3/8 and 2-3/4 inch -- verify before assuming
Why This Matters More Than It Looks on Paper
The Strike Has to Line Up
The latch backset and the strike location are linked. When a door is prepped for 2-3/8 inch and the lockset shipped is 2-3/4 inch, the bolt face lands 3/8 inch short of the strike pocket. The door may close but will not latch -- or the bolt will rub the frame face instead of projecting cleanly into the strike box. In fire-rated assemblies, a door that does not positively latch is a failed inspection and a life-safety deficiency under NFPA 80.
The Rose Plate and Edge Clearance
On a 2-3/8 inch prep, installing a 2-3/4 inch lockset moves the lever rose outward from the edge -- that gap is cosmetically acceptable on some doors. The reverse is worse: a 2-3/8 inch lockset on a 2-3/4 inch prep shifts the rose toward the frame, potentially interfering with the frame stop and preventing the door from closing fully.
Latch Front Width and Mortise Depth
The latch front (the face plate on the door edge) also changes width between the two standards. A 1 inch wide latch front is typical on 2-3/8 inch latches; 1-1/8 inch fronts appear on many 2-3/4 inch commercial latches. If the door is already mortised for one width and you install the other, the front plate either overhangs or leaves a gap -- both are problems on fire-rated assemblies where the front must seat flush.
How to Confirm the Right Backset Before Ordering
- Read the door prep sheet. Pre-bored hollow metal doors will call out the backset on the door schedule or the manufacturer's prep sheet. Do not assume.
- Measure the existing door if replacing a lockset. Measure from the door edge face to the center of the existing cross bore -- that is the actual backset.
- Check whether the latch is adjustable. Many commercial cylindrical locksets ship with a latch that slides to cover both dimensions. The latch body locks into position with a clip or screw. Confirm this on the template sheet before ordering a separate latch.
- Verify the strike prep on the frame. The strike location in the frame must match the latch backset. If you are replacing hardware in an older building, the frame prep may be the 2-3/8 inch dimension even if the new lockset defaults to 2-3/4 inch.
- Use the manufacturer template. Every commercial cylindrical lockset ships with or links to a prep template. Corbin Russwin, Accentra, Sargent, and Hager all publish separate templates for each backset. Match the template to the door prep before drilling anything.
Common Field Scenarios
School Renovation -- Replacing Classroom Locks in Older Buildings
Many school buildings from the 1960s through the 1980s were built with residential-origin 2-3/8 inch preps on interior wood doors. When a facility team orders new Grade 1 classroom security locks from a preferred commercial line such as Corbin Russwin or Sargent, the default ships at 2-3/4 inch. Confirm the door prep before the order ships or specify an adjustable latch at time of purchase.
Healthcare Construction -- New Hollow Metal Doors
New hollow metal doors for patient room corridors are nearly always prepped to 2-3/4 inch as the commercial standard. Hardware schedules for healthcare projects should call out backset explicitly to avoid substitution errors during submittal review.
Retail and Light Commercial -- Pre-Hung Wood Doors
Interior pre-hung wood doors in tenant finish-out are frequently bored at 2-3/8 inch from the door manufacturer. If the spec calls for a commercial cylindrical lock, confirm the latch backset before the hardware order is placed -- this is one of the most common field misfits on light commercial tenant improvement projects.
Specifying It Correctly on a Hardware Schedule
When writing or reviewing a hardware schedule for cylindrical locksets, include the backset dimension as a line item in the lockset description. Do not leave it to the installer to figure out on the jobsite. A line that reads "cylindrical lockset, Grade 1, classroom security function, 2-3/4 inch backset, 2-1/8 inch cross bore, 1 inch edge bore" eliminates the ambiguity that causes reorders and installation delays.
DoorwaysPlus carries commercial cylindrical locksets from Corbin Russwin, Accentra (formerly Yale), Sargent, Hager, and PDQ -- lines known for consistent prep dimensions and stable parts availability. If you are not sure which backset your door is prepared for, our team can help you verify before the order ships.