Door Lock Backset: How to Measure Before Replacing a Lock

A replacement lock can look right and still fail to fit. Backset is the distance from the door edge to the centre of the cross-bore—the large hole for a knob or lever. For a tubular or cylindrical lock, measure straight from the latch-side edge (where the latch faceplate sits) to the centre of that hole. Schlage’s guide shows this method.

How to measure

With the door open, hold a ruler level across the face and measure from the edge to the centre of the existing handle hole. Record the result in millimetres, then check whether the replacement latch has a fixed or adjustable backset. Schlage lists 2⅜ in (about 60 mm) and 2¾ in (about 70 mm) for its own residential locks—examples, not universal Pakistani sizes. If you measure about 60 mm, don’t assume a fixed 70 mm latch will fit.

Check more than backset

Also note door thickness, lock type, latch or mortise-body dimensions, faceplate shape, and spindle/screw positions. A mortise lock has a different case and cut-out, so backset alone is not enough. Before ordering, compare measurements with the product’s own specification or ask Jinnah’s store team to confirm fit. Browse the Door Hardware & Security collection, and verify the chosen item’s current specifications and availability.