How to Measure a Euro Cylinder

A euro cylinder is the barrel-shaped locking mechanism fitted inside the lock case on most uPVC and composite front doors, as well as many back doors and French doors. It is the part that your key turns, and it is held in place by a single central screw through the door handle faceplate. Because it is designed to be removable and interchangeable, it is also the part that burglars exploit when the cylinder sticks out too far beyond the door face. By gripping the protruding section with a pair of pliers and applying sharp downward force, they can snap the cylinder in seconds and push the broken stub inward to operate the cam directly. This is called cylinder snapping, and it requires no specialist skill whatsoever.

The defence against it is straightforward: fit a cylinder that is the correct length for your door, and choose one rated to the TS007 3-star standard or carrying an anti-snap designation. Neither of those things is possible if you do not first know your exact measurements. A cylinder that is even five millimetres too long on the external side can be enough to make snapping viable, so precision here genuinely matters.

You will need a flat-head screwdriver to remove the central retaining screw, and a steel ruler or tape measure. Start with the door closed and locked in the normal position. Locate the screw in the centre of the door handle escutcheon or faceplate — this is usually a single cross-head or flat-head screw sitting between the handle and the keyhole. Undo it and keep it somewhere safe. The cylinder will not fall out at this stage; it is still held by the cam mechanism inside the lock case.

Now measure from the centre of the central screw hole to each end of the cylinder. The measurement to the outside face of the door (the side facing the street) is called the external measurement, and the measurement to the inside face is the internal measurement. Write both down. A typical cylinder on a standard uPVC door might read 35mm external and 45mm internal, written as 35/45 and totalling 80mm overall — but doors in older Bermondsey terraces, converted warehouse flats near Tower Bridge Road, and modern new-builds on the Old Kent Road corridor all vary considerably, so always measure your specific door rather than guessing from a standard. The external figure is the critical one for snapping resistance: ideally it should be flush with or no more than 3mm proud of the outer door face once the cylinder is fitted. If your current cylinder protrudes more than that, it should be replaced as a priority.

Once you have your measurements, you need to decide on the type of cylinder. For any exterior door in a residential property, the minimum sensible choice is a cylinder that meets the TS007 3-star standard or is independently rated as anti-snap, anti-pick, anti-drill, and anti-bump. These cylinders have a sacrificial snap point engineered into them: if someone attempts to snap the external portion, the break happens before the security pins are reached, leaving the lock fully intact and the door secure. The difference between a basic cylinder and a quality anti-snap one is significant in a real-world attack scenario, and your home insurer may specifically ask whether you have a BS3621 compliant lock arrangement on your front door — the cylinder is part of that picture.

If you are in a rented flat, it is worth checking your tenancy agreement before changing the cylinder yourself. Most letting agents and housing associations in Bermondsey require that any lock change London is carried out by a qualified professional and that a copy of the new key is provided to the landlord within a set timeframe. Failing to follow that process can complicate things if you later lose keys or need emergency access. If you are unsure, our team can advise you on the right approach and liaise with managing agents where needed. For door lock replacement London on uPVC and composite doors, we carry a range of correctly sized, security-rated cylinders and can confirm the right specification before any work begins.

Swapping a euro cylinder on a straightforward uPVC door is well within the capabilities of a confident homeowner who has the right measurement and the correct replacement part. However, there are several situations where calling an experienced locksmith London is the right decision. If the cylinder has already been snapped or damaged, the internal cam may also be broken, meaning the lock case itself needs attention — not just the cylinder. If the door has a multipoint locking system and the cylinder has seized, forcing it out can damage the gearbox inside the door, turning a simple cylinder swap into a full upvc door lock repair London. If you are locked out London and cannot access the cylinder from the inside at all, a professional can often open the door without damaging the frame or the lock, which protects the security of the door going forward.

Similarly, if you are asking yourself questions like how to change a lock on a door you have never worked on before, or how to change door lock components on a composite door where the tolerances are tighter, it is worth getting a professional opinion first. A skilled locksmith can assess whether the existing lock case is compatible with a new cylinder, check the door alignment, and confirm that the final setup genuinely meets security standards — not just that it functions. We are available across Bermondsey and the wider SE1 area around the clock, so if you would like a professional to take a look, call 020 7871 2569 and we will send someone straight out to you, usually arriving within about 30 minutes.

Measuring and fitting the right euro cylinder is an important step, but it sits within a broader picture of door security. Most front doors in Bermondsey benefit from having both a Yale-type nightlatch and a 5-lever mortice deadlock — insurers frequently ask for BS3621 on the mortice lock specifically. If your door relies on the euro cylinder alone, that is worth raising with an experienced locksmith during any visit. For uPVC and composite doors, the multipoint locking system does a lot of the heavy lifting, but only if the door is properly aligned and the keep (the metal plate in the door frame) is securely fixed. Misaligned doors, common in older converted flats and Victorian terraces across the Bermondsey and Borough area, can mean the hooks and bolts do not engage fully even when the door appears locked.

It is also worth thinking about what happens if someone attempts to pick rather than snap your lock. Quality anti-snap cylinders are also engineered to resist picking, but a basic cylinder offers very little resistance to someone who has practised. If you have ever wondered how to pick a door knob lock or how to pick a lock generally, the honest answer is that standard cylinders are more vulnerable than most people expect — which is exactly why upgrading to a security-rated cylinder matters. The good news is that a properly specified replacement, fitted at the correct length, addresses snapping, picking, drilling, and bumping in a single change. As a 24 hour locksmith London, we can carry out that upgrade at any time, day or night, evenings, weekends and bank holidays included. Call 020 7871 2569 — we answer 24/7.

As a mobile emergency locksmith London, we cover a wide range of residential and commercial lock work across Bermondsey, SE1, and the surrounding areas. Our services include: euro cylinder measurement and replacement, anti-snap cylinder upgrades, TS007 3-star cylinder fitting, 5-lever mortice deadlock installation (BS3621), Yale nightlatch fitting and replacement, multipoint lock repair, multipoint lock replacement, uPVC door lock repair, composite door lock repair, wooden door lock fitting, door handle and escutcheon replacement, lock change London for residential properties, door lock replacement London for uPVC and composite doors, emergency locksmith London call-outs for locked out London situations, non-destructive entry where possible, lock snapping damage repair, door frame and keep repair after a break-in, letterbox security upgrades, door reinforcement fitting, thumb-turn cylinder fitting for interior use, communal entrance lock servicing for blocks of flats, landlord lock change between tenancies, lock change for letting agents and housing associations, keypad door lock installation, and security surveys to identify weak points across the whole door set. Every job starts with a conversation about what you need and a clear, confirmed price before we begin any work.

We do not publish fixed prices because the cost of any lock job depends on several honest variables: the type of lock and cylinder required, the make and age of the door, the time of day (evening, weekend, and bank holiday call-outs reflect the hours worked), the travel distance to your property, and whether any additional parts or repair work are needed beyond the initial cylinder swap. What we do commit to is confirming an exact up-front price with you over the phone before anyone leaves to come out. There are no surprise figures on arrival. If the job turns out to be more involved than first described — for example, if a damaged lock case is discovered once the cylinder is removed — we will explain what has been found and confirm any revised cost before proceeding. That approach protects you and allows you to make an informed decision at every stage.