How to Measure and Replace a Euro Cylinder Lock
At a Glance - What You’ll Learn
- How to remove an existing Euro cylinder
- How to measure it accurately
- How to install a replacement correctly
- Tips to avoid common mistakes (alignment, getting the right size)
Tools & Materials Needed
- Screwdriver (typically Phillips)
- Tape measure or ruler
- Replacement Euro Cylinder
- Key for the existing cylinder
1. Remove the old
Assuming you are replacing an existing lock - the current euro cylinder will be held in place with a central screw that is located on the face edge of the door. To remove the lock, you need to first remove this central screw.
Once removed, insert the key and turn 45 degrees either left or right (depends on which side you insert the key).
To find the "sweet spot" where the cam shaft lines up with the cylinder body (allowing it to pull free of the door), with the key inserted, try turning it and pulling the lock gently towards you. When it aligns you'll feel the lock start moving.
You need to turn the key as the central cam is offset when the key is removed and prevents you from removing the cylinder. Turning the key 45 degrees will align the cam flush with the cylinder body and allow you to remove it from the door.
If you turned the key the right amount and direction the lock will start to move and slide out the door.
2. Measure
When measuring for a Euro Cylinder the easiest way is measure the one you are replacing.
Measure from one end of the cylinder to the centre of the central screw hole, then repeat the process for the other side. This will give you the size of cylinder you need to match.
You need to measure both halves of the cylinder as some cylinders are offset so the 2 halves are different lengths.
3. Install
Once you have your replacement, simply repeat Step 1 in reverse.
- Insert the key and turn the cam shaft so it is flush with the cylinder body.
- Insert the cylinder into the door - if you have the correct sized cylinder, inserted the correct way round, you will align the central screw hole in the cylinder with the corresponding hole in the face edge of the door.
- Insert the fixing screw through the face edge of the door into the cylinder's central screw hole. Tighten the screw to fix the lock in place.
Security & Upgrade Tips
- Choose British Standard, at least 1 Star cylinders for exterior doors
- Match cylinder size to door thickness (see above video for details)
- Too much cylinder protruding increases risk of snapping
Relevant Euro Cylinder Categories
British Standard Cylinders - suitable for external doors
Double cylinders - wide range of door sizes
Thumbturn cylinders - easy internal egress (safer for external doors)
Smart cylinders - keyless access and app based access management
Frequently Asked Questions – Euro Cylinder Installation
How do I know what size Euro cylinder I need?
Remove your existing cylinder and measure from the centre of the fixing screw to each end of the barrel. This will give you two measurements in millimetres, for example 35/35 or 40/50. Always measure both sides, as some cylinders are offset.
What does 35/35 or 40/50 mean?
Euro cylinders are measured from the centre fixing screw outwards. A 35/35 cylinder means both sides are 35mm from the centre. A 40/50 cylinder means one side is 40mm and the other is 50mm. The first number is usually the internal side, and the second is the external side.
Can I replace a Euro cylinder myself?
Yes. Replacing a Euro cylinder is a straightforward DIY task for most homeowners. You only need a screwdriver and a tape measure. Always ensure the door is open when removing the cylinder to avoid locking yourself out.
Why won’t my Euro cylinder come out?
Even after removing the central fixing screw, the cylinder will not slide out unless the cam is aligned. Insert the key and turn it slightly until the cam lines up with the body of the cylinder. You may need to gently pull while adjusting the key position.
In some cases, the escutcheon or lock body may have been fitted tightly or shifted over time, putting pressure on one side of the cylinder. If the cylinder will not slide out freely, loosen the handle or escutcheon to relieve the pressure. Avoid hitting the cylinder with a hammer or mallet.
What is an offset Euro cylinder?
An offset cylinder has different internal and external measurements, such as 35/45. These are common where door thickness or handle depth differs on each side.
How far should a Euro cylinder stick out?
Ideally, a cylinder should sit flush with the handle or escutcheon plate. If it protrudes more than a couple of millimetres, it may be more vulnerable to snapping or forced entry. Aim for a maximum protrusion of 3mm.
Should I upgrade to an anti-snap cylinder?
For external doors, especially uPVC or composite doors, we strongly recommend upgrading to at least a British Standard 1-star Euro cylinder. These provide significantly improved protection against common forced entry methods.
What’s the difference between 1-star and 3-star cylinders?
A 3-star cylinder provides the highest standalone level of protection. A 1-star cylinder may require a 2-star handle to achieve equivalent protection. For simplicity and maximum security, many customers choose a 3-star cylinder.
Do I need to remove the whole lock to change a Euro cylinder?
No. You only need to remove the central fixing screw on the edge of the door. The lock mechanism stays in place.