What Size Locks and Latches Do I Need?

Door Lock Diagram

Tubular Latches, Sashlocks, Deadlocks and Bathroom Locks are available in varying lengths and sizes to suit your requirements or match existing ones already fitted in your doors.

When replacing your door handles we always recommend changing the internal latches and locks with our units for the following reasons; Firstly they have probably become warn and could possible fail when newer handles are fitted. The internal springs and follower (square hole where the bar goes through) will fatigue and eventually snap potentially stopping the door from being opened. Secondly the latches might have a different throw which will put increasing strain on the springs inside the handle and prematurely wearing them out. 

We are often asked the question "What size latches and locks do I need?".

Replacing locks and latches in your existing doors - you will probably want to replace them with the same size, this way you will avoid having to carry out any unnecessary work.

Fitting locks and latches to new or replacement doors - you are free to use the size that is most suitable for the door and the door furniture being fitted.

Remember that the size of the latch or lock will determine where your door handle or door knob will end up on your door, so if you have a panelled door and you want your door furniture to sit nicely in the centre of the stile, or you have deep frame stops, you need to choose the correct size lock or latch with the correct backset to accommodate this. The 'Backset' is the measurement between the forend plate and the centre of the keyhole or follower (Square hole that the spindle goes through).

Frame stop clearance - the backset of a lock or latch must ensure that the door furniture fitted to it is clear of the frame stop when the door is closed.

Knuckle rash! - there must be room for the hand to operate the door furniture without interference from the frame stop, especially important when fitting door knobs.


Examples of current metric backsets on locks and latches

Lock/Latch Size Backset
64mm 45mm
76mm 57mm
102mm 84mm
127mm 109mm
152mm 134mm


Measuring the backset with lock or latch fitted in the door

If you are replacing existing locks and latches with like for like sizes but the existing ones are still fitted in the door.

You can work out the size of the lock by measuring the distance from the edge of the door to the centre of the door handle or knob.

This measurement will give you the approximate size of the backset which will allow you to identify which size lock or latch you have.

Backset Diagram

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