How to Measure a Euro Cylinder Lock – Complete UK Size Guide
Choosing the correct replacement door cylinder is essential for both security and reliable lock operation. Whether you're replacing a worn cylinder, upgrading to an anti-snap lock or ordering a new Mul-T-Lock cylinder, accurate measurements will help ensure you receive the correct size.
Euro profile cylinders are widely used in UPVC, composite, aluminium and timber doors. They are available in different lengths, configurations and security levels, so it's important to check more than just the overall cylinder length.
At Garrison Locks, we have over 35 years of locksmith industry experience. This guide explains how to measure a euro cylinder lock correctly, identify the external and internal measurements, select the correct thumbturn configuration and avoid common ordering mistakes.
What Is a Euro Profile Cylinder?
A euro profile cylinder is the removable locking component fitted through a compatible door lock case or multipoint locking mechanism.
It is operated by a key, or by a combination of a key and thumbturn, depending on the cylinder design.
Euro cylinders are commonly found in:
UPVC and composite entrance doors.
Timber and aluminium doors.
Multipoint locking systems.
Commercial entrance doors.
Certain mortice lock cases and security applications.
Although many euro cylinders share a standard profile, their lengths and operating configurations vary.
The replacement cylinder must be the correct size and type for your existing door and lock mechanism.
How to Measure a Euro Cylinder Lock
Euro cylinders are measured from the centre of the cylinder's fixing screw hole to each end of the cylinder.
This produces two measurements, usually referred to as A and B.
For example, a cylinder measuring 35mm on one side and 45mm on the other is described as a 35/45mm euro cylinder.
Its total length is 80mm.
Step 1 – Open the Door
If you are removing an existing cylinder, open the door and ensure it is safe to work on.
The cylinder retaining screw is normally visible on the edge of the door, in line with the cylinder.
Do not attempt to remove a cylinder from a locked door if you are unsure how the mechanism operates.
Step 2 – Remove the Existing Cylinder
Remove the cylinder retaining screw using a suitable screwdriver.
Insert the key and turn it slightly to align the cam with the cylinder body. The cylinder should then slide out without excessive force.
If the cylinder does not move, check that the cam is correctly aligned and that no other fixings are preventing removal.
Never force the cylinder out of the door.
Step 3 – Measure the Outside Length (A)
Place the cylinder on a flat surface.
Using a ruler or measuring tape, measure from the centre of the fixing screw hole to the outside end of the cylinder.
For example:
A = 35mm
Step 4 – Measure the Inside Length (B)
Measure from the centre of the same fixing screw hole to the opposite end of the cylinder.
For example:
B = 45mm
Step 5 – Confirm the Total Length
Add both measurements together.
35mm + 45mm = 80mm
Your cylinder would therefore be described as a 35/45mm euro cylinder.
Remember to identify which measurement belongs to the external side and which belongs to the internal side of the door.
This is particularly important when ordering thumbturn cylinders or products with different security features on each side.
Euro Cylinder Size Chart
Euro cylinders are manufactured in a range of lengths to accommodate different door thicknesses and handle arrangements.
The following examples illustrate commonly encountered configurations.
| Cylinder size | Side A | Side B | Total length |
|---|
| 30/30 | 30mm | 30mm | 60mm |
| 30/35 | 30mm | 35mm | 65mm |
| 35/35 | 35mm | 35mm | 70mm |
| 35/40 | 35mm | 40mm | 75mm |
| 35/45 | 35mm | 45mm | 80mm |
| 40/40 | 40mm | 40mm | 80mm |
| 40/45 | 40mm | 45mm | 85mm |
| 40/50 | 40mm | 50mm | 90mm |
| 45/50 | 45mm | 50mm | 95mm |
| 50/50 | 50mm | 50mm | 100mm |
These are examples rather than a complete list of available sizes. Individual manufacturers and cylinder platforms may offer different size combinations.
Equal and Offset Euro Cylinders – What's the Difference?
Not all euro cylinders have equal measurements on both sides.
Equal Cylinders
An equal cylinder has the same measurement on each side of the fixing screw.
For example:
35/35mm = 70mm overall
These are often used where the lock case is centrally positioned within the door and the external and internal furniture have similar dimensions.
Offset Cylinders
An offset cylinder has different measurements on each side.
For example:
35/45mm = 80mm overall
Offset cylinders are common on Composite and Upvc doors where the door thickness or handle arrangement requires a longer cylinder section on one side.
Always check the orientation before ordering, particularly when the cylinder has a thumbturn or an external security feature.
How to Measure a Euro Cylinder Without Removing It
In some situations, you may be able to establish the required cylinder dimensions without removing the existing lock.
With the door open, locate the cylinder retaining screw on the door edge.
Measure from the centre line of that screw to the outer face of the external handle or escutcheon, then repeat on the internal side.
These measurements help establish the required cylinder lengths, allowing for the manufacturer's recommended projection.
However, measuring the installed cylinder is not always as accurate as removing it, particularly where the door furniture is recessed, unusually thick or fitted with protective security components.
For the most accurate result, measure the existing cylinder after removal whenever practical.
How Far Should a Euro Cylinder Protrude from the Door?
Correct cylinder length is important for security as well as appearance.
A cylinder that projects excessively beyond the external handle or escutcheon may be more vulnerable to physical attack.
As a general security principle, the cylinder should sit as close as practical to the external face of the protective door furniture.
A commonly recommended maximum projection is approximately 5mm, although the correct arrangement depends on the cylinder, handle design and manufacturer's installation requirements.
Do not assume that a longer cylinder is acceptable simply because it operates the lock.
Where protective security handles or escutcheons are fitted, follow the manufacturer's specified cylinder dimensions and installation instructions.
Key and Key vs Key and Thumbturn Cylinders
Euro cylinders are available in several operating configurations.
Double Euro Cylinders – Key and Key
A double euro cylinder is operated using a key from both sides.
These are commonly described as:
Key and key cylinders.
Double euro cylinders.
Double-ended cylinders.
They are available in equal and offset sizes.
Key and Thumbturn Euro Cylinders
A thumbturn cylinder is operated by a key on one side and a thumbturn on the other.
Thumbturn cylinders are commonly used where convenient keyless operation from the inside is required.
When ordering, it is important to specify which side requires the thumbturn.
For example, a 45/50V cylinder may indicate that the thumbturn is positioned on the 50mm side, depending on the manufacturer's product coding.
Always check the supplier's measurement convention before ordering.
For doors used as emergency escape routes, the cylinder and locking arrangement must be appropriate for the relevant fire safety and escape requirements.
What About Half Euro Cylinders?
Half euro cylinders have one operating side and are commonly used in applications such as:
Roller shutter keyswitches.
Garage door locks.
Certain access control systems.
Electrical switch mechanisms.
Specialist commercial locking products.
Unlike a standard double euro cylinder, a half cylinder has a single operating side and a shorter body arrangement.
When ordering a replacement half cylinder, check:
The overall cylinder length.
The operating-side measurement.
The cam type.
Whether a standard or adjustable cam is required.
Compatibility with the existing lock or keyswitch.
Some half euro cylinders are supplied with variable-position cams for specialist applications.
Do not assume that all half euro cylinders are interchangeable.
How to Measure an Oval Cylinder
Oval profile cylinders are also used in certain commercial and specialist locking applications.
Although the measuring principle is similar, an oval cylinder is not interchangeable with a euro profile cylinder.
Measure from the centre of the fixing screw position to each end of the cylinder, following the manufacturer's dimensional convention.
You should also confirm the cylinder profile, cam configuration and compatibility with the existing lock case.
If your door uses an oval cylinder, order the appropriate oval profile replacement rather than a euro cylinder of similar length.
Choosing a High-Security Replacement Cylinder
If you're replacing an existing cylinder, it may be worth considering an upgrade to a higher-security product.
Depending on your door and security requirements, options include:
Anti-Snap Euro Cylinders
Anti-snap cylinders are designed to provide enhanced resistance to certain methods of physical attack.
Look for recognised certification appropriate to the product, such as TS007 3 Star or Sold Secure SS312 Diamond, where relevant.
Mul-T-Lock Cylinders
Mul-T-Lock offers a range of mechanical cylinder platforms for domestic, commercial and specialist applications.
Depending on the selected platform, options may include restricted key control, keyed alike arrangements and master key systems.
Keyed Alike Cylinders
Keyed alike cylinders allow multiple compatible locks to be operated using the same key.
This can be particularly useful for homes, commercial premises and buildings with several entrance doors.
Master Key Systems
Master key systems provide structured access control using different key levels, allowing designated keys to operate specific groups of cylinders.
Garrison Locks supplies specialist cylinder and master key solutions for a wide range of applications.
Common Mistakes When Ordering Replacement Cylinders
Before placing an order, avoid these common mistakes:
Measuring only the total length. Two cylinders can have the same overall length but different A and B measurements.
Reversing the external and internal sizes. This is especially important with thumbturn cylinders and asymmetric security designs.
Allowing excessive cylinder projection. A cylinder should be correctly sized for the door and protective furniture.
Ordering the wrong profile. Euro, oval and other cylinder profiles are not automatically interchangeable.
Overlooking the cam configuration. Specialist lock cases and half cylinders may require particular cam types.
Choosing the wrong key system. Check whether you require keyed alike, keyed different, restricted keys or compatibility with an existing master suite.
Assuming all manufacturers offer identical sizes. Available dimensions and ordering conventions can vary between cylinder ranges.
Frequently Asked Questions
What does 35/45 mean on a euro cylinder?
It means the cylinder measures 35mm from the centre fixing screw to one end and 45mm from the centre fixing screw to the other end, giving a total length of 80mm.
Are euro cylinders measured including the thumbturn?
Euro cylinder body measurements normally refer to the cylinder length, not the projecting thumbturn knob. Always check the manufacturer's dimensional diagram.
Can I replace a 35/45 cylinder with a 40/40 cylinder?
Both have an overall length of 80mm, but the dimensions on each side are different. They should not be treated as interchangeable without checking the door and handle arrangement.
Are euro cylinders universal?
Many euro cylinders share a standard profile, but their lengths, cams, security features and operating configurations vary. Compatibility must be confirmed before ordering.
Should a euro cylinder sit flush with the handle?
The external cylinder should sit as close as practical to the protective furniture, in accordance with the manufacturer's recommendations. Excessive projection should be avoided.
Can I order several cylinders that work with one key?
Yes. Many cylinder ranges are available in keyed alike configurations, subject to the manufacturer's key platform and product compatibility.
Buy Replacement Euro Cylinders from Garrison Locks
Garrison Locks supplies a wide range of euro profile cylinders, high-security locking products and specialist key systems for domestic and commercial applications.
Our range includes:
Euro profile key and key cylinders.
Euro profile key and thumbturn cylinders.
Half euro cylinders.
Anti-snap and high-security cylinders.
Mul-T-Lock cylinders.
Oval profile cylinders.
Keyed alike and master key systems.
Whether you need a straightforward replacement or a more advanced security solution, choosing the correct cylinder size and configuration is essential.
Browse our cylinder range or contact our team for help identifying the correct product.
Need Advice? Contact Garrison Locks
At Garrison Locks, we have over 35 years of experience in the locksmith and security industry. If you're unsure which cylinder size, key platform or configuration you require, our knowledgeable team can help.
Garrison Locks Ltd
Telephone: 01858 464 133
Email: enquiries@garrisonlocks.co.uk
Website: https://garrisonlocks.co.uk
Garrison Locks – Your UK Specialist in Security, Locks & Access Solutions.
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