Home lock calculator
Door Bore Hole Compatibility Checker
Compare your face bore and edge bore measurements with common lock preparation.
Result
Edge deviation from 1 in
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Face deviation from 2-1/8 in
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Edge bore match (1 = yes)
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Face bore match (1 = yes)
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Formula
Calculation logicUse the exact installation template for the lock you plan to install.
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
- Check face and edge bores separately
- Look for chipped paint or misalignment
- Never freehand a new bore