Home lock calculator
Deadbolt Backset Measurement Checker
Identify a common 2-3/8 inch or 2-3/4 inch deadbolt backset.
Result
Deviation from nearest standard (in)
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2-3/8 in match (1 = yes)
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2-3/4 in match (1 = yes)
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Formula
Calculation logicMeasure from the door edge to the center of the bore hole. Do not measure to the trim edge.
Backset and Latch Faceplates, Explained
The two US backsets
Residential doors use 2-3/8 in or 2-3/4 in, measured edge to hole center. Adjustable latches cover both; fixed latches do not.
Match the faceplate
- Round corner: most common retrofit.
- Square corner: older and commercial doors.
- Drive-in: no plate; the latch presses into the bore.
Wrong plate means chiseling. Bring the old latch to the store when in doubt.
How to Measure Door-Lock Prep
Take these four readings first
- Door thickness. Calipers on the slab edge, three spots, keep the largest. Stock locksets cover 1-3/8 to 1-3/4 in.
- Face bore. Tape across the widest point of the large hole. US standard is 2-1/8 in.
- Edge bore. The small latch hole is 1 in on standard prep.
- Backset. Door edge to bore-hole center: 2-3/8 or 2-3/4 in.
Photograph before you shop
One photo per reading, plus a wide shot of hinges and strike. A locksmith can quote from photos; a purchase cannot be returned once a door is drilled.
Verify before you buy
- Measure twice: top and middle of the hole
- Photograph the tape seated on the door edge
- Buy adjustable when between sizes