How to Identify uPVC Window Handles: A Complete UK Guide

Almost all doors in the UK will have a euro cylinder installed in them, whether it's a uPVC, composite, or timber door. And like most locks, most households will need to replace one at some point, whether due to wear and tear, lost keys, or a security upgrade. 

Choosing the correct measurements is crucial to ensure your new cylinder fits properly and your door remains secure. To help you find the right fit, here is our comprehensive guide to teach you how to measure a euro cylinder door lock accurately.

How to Measure My Door Lock Euro Cylinder?

Measuring a euro cylinder is straightforward when you know what to look for. To measure your euro cylinder lock, you'll need a tape measure or ruler and follow these simple steps:

Step-by-Step Euro Cylinder Measuring Guide:

1. Remove the cylinder (optional but recommended for accuracy): Remove the fixing screw located on the edge of your door, insert the key and turn it approximately 25 degrees to align the cam, then gently pull the cylinder out.
2. Locate the centre screw hole: This is the fixing point where the screw secures the cylinder to your door lock mechanism.
3. Measure from centre to outside edge (Measurement A): Measure from the centre of the screw hole to the outer edge of the cylinder on one side.
4. Measure from centre to the other outside edge (Measurement B): Measure from the centre of the screw hole to the outer edge on the opposite side.
5. Calculate the total length (Measurement C): Add measurements A and B together. For example, a 40/40 cylinder would be 80mm in total length.

Important: The measurements for A and B should equal C if you've measured your cylinder correctly. The two measurements (A and B) make up the complete size specification of your door lock.

Common Euro Cylinder Sizes:

Euro cylinders are available in various sizes to suit different door thicknesses and handle positions. Common sizes include:

• 30/30 (60mm total)
• 35/35 (70mm total)
• 40/40 (80mm total)
• 35/45 (80mm total)
• 40/50 (90mm total)

Asymmetrical sizes (such as 35/45) are often required when the door handle or lock is positioned off-centre.

Do Cylinders Have an Internal and External Side?

Along with general length, you will also need to look at each side. This measurement is crucial for correct installation and security.

Standard Double-Key Cylinders:

Most standard euro cylinders, which use a key on both sides, do not have a specific internal or external side. They are reversible and can be installed either way round, making installation straightforward and flexible.

Thumb Turn Cylinders:

A euro cylinder thumb turn, which uses a thumb turn knob on the internal side of the cylinder, does have specific sides. The thumb turn mechanism must face inwards for convenient exit without needing a key. When measuring a thumb turn cylinder, you must ensure you make note of which measurement (A or B) corresponds to the internal side, as this cannot be reversed during installation.

High-Security Cylinders:

High-security cylinders may also have a specific external side. This is because all of the security features—including anti-snap, anti-drill, and anti-pick mechanisms are installed on the external half of the cylinder to protect against forced entry attempts. 

If you’re looking to replace or upgrade your cylinder with a high-security cylinder, double-check whether that cylinder has a specific external side to ensure the best protection.

Tips for Accurate Measurement:

• Measure twice to ensure accuracy: A small error can result in ordering the wrong size.
• Consider the handle or escutcheon depth: Your cylinder shouldn't protrude more than 3mm beyond the door furniture, as this can create a security vulnerability.
• Take photos: When in doubt, photograph your existing cylinder with a ruler for reference.
• Check the security rating: While measuring, consider upgrading to a TS007 3-star rated cylinder for enhanced security.

Where to Buy Euro Cylinder Locks:

We stock a full range of quality euro cylinders from trusted brands such as Yale and Versa, including standard cylinders, thumb turn cylinders, and high-security options with TS007 certification. All our cylinders come with clear sizing information and fitting instructions. If you’re ready to make the change, take a look at our full range of uPVC door lock barrels.

Whether you're replacing a worn cylinder, upgrading your home security, or need keyed-alike cylinders for multiple doors, GB DIY Store has the right solution at competitive prices with same-day dispatch available on orders placed before 3 PM. For more information, take a look at our locks or contact our team today to get some advice on what you need.