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How do you measure for a door latch / lock?

Measuring for a door latch / lock:

Ever wondered how to measure for a door latch or lock? We get lots of requests for door handles, door knobs and other door furniture but more often than not, when we ask “What size latch / lock do you need?”, the answer is uncertain.

But fear not, it’s actually very easy to know which size latch you need. But first, let’s look & understand the terminology.


  • Stile – The vertical “space” available on a door. See image #1.
  • Rail – The horizontal “space” available on a door. See image #1.
  • Case – Full measurement for the latch. The most common UK case sizes are 63mm (2.5”) and 76mm (3”). These have historically been listed in inches; however, it’s becoming more common to use millimeters instead. See image #3.
  • Body – Thickness of the latch, usually a standard of 25mm faceplate and 14mm-15mm interior.
  • Spindle – The “bolt” that goes from one handle / knob to the other side of the door. This operates the latch and allows for opening and closing.
  • Backset – The measurement between the faceplate of the latch, to the spindle hole. See image #3.

Step 1:

Decide on where you want the door handle or knob to be positioned. Take into consideration if your door has any panels, patterns or detailing which might restrict the available space on the door. (The latch case needs to fit inside the stile and/or rail without overlapping any door panels or detailing)

As seen in image #2, lever handles can be positioned closer to the edge of the door as their input is vertical, whereas knobs are rotational and require more space to avoid scraping your knuckles against the door frame.

It’s also worth noting if your chosen door handle or knob has a backplate which will need accounting for in the positioning phase.

Step 2:

Once you’ve decided where you want the handle or knob to be positioned, it’s time to measure which sized latch is suitable for your preference. The backset of the latch is what needs to align with your handle positioning. See image #5 on how the interior of your door should look.

Remember to account for any backplates that your handle may have, as the HANDLE FITS THE LATCH. And not the other way around.

Below is a table of UK Standard latch / lock sizes:

 Case Size


 51mm (2”)


 63mm (2.5”)


 76mm (3”)


 101mm (4”)



Step 3:

Now, you need to make sure that:

  1. There’s room in the door stile / rail to fit a full case lock
  2. You’ve accounted for any backplates on your knob / handle
  3. You are confident the handle, latch case size and door are compatible with each other

and once you've ticked those boxes... You’re done! Now you're able to view our range of Locks, Latches & Cylinders and make the correct decision on which latch you should be purchasing.

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