How to Measure a Euro Cylinder

A euro cylinder is the oval-shaped barrel that sits inside the lock housing on most uPVC and composite front doors across London and the South East. If your door has a multipoint locking mechanism — meaning you lift the handle to engage multiple locking points before turning the key — there is almost certainly a euro cylinder doing the work at the keyhole. The same applies to many timber doors fitted with a modern multipoint lock. What you see from the outside is a small oval plate with a keyhole; the cylinder behind it runs straight through the door, with a section on the outside, a section on the inside, and a small cam in the centre that connects to the locking mechanism.

In Abbey Wood and the wider SE2 area, a large proportion of the housing stock — including many of the terraced and semi-detached homes near Knee Hill, the flats along Harrow Manorway, and the newer-build properties closer to the Crossrail station — uses uPVC or composite doors as standard. That means euro cylinders are extremely common here. Understanding how to measure one is a genuinely practical skill, because an incorrectly sized replacement either will not operate the lock at all, or — far more dangerously — will protrude enough from the door face to invite a technique called cylinder snapping.

You need only a tape measure or a flat ruler. Start by opening your door fully so you can examine the lock edge clearly. Look at the faceplate on the edge of the door — the narrow metal strip running vertically — and find the small screw that runs horizontally through the centre of it. That screw holds the cylinder in place and also tells you where the centre point of the cylinder sits. With the door open, measure from the outer face of the door (the side that faces the street) to the centre of that retaining screw. Write that number down — this is your external measurement, often written as the first number in a cylinder size, for example 35 mm. Now measure from the inner face of the door to the centre of the same retaining screw. Write that number down too — this is your internal measurement. Add a small allowance of around 5 mm to each figure to account for the door furniture (the handle plate or escutcheon that sits proud of the door surface). So if your raw measurements are 35 mm outside and 45 mm inside, you would look for a 40 x 50 cylinder. The total figure — both numbers added together — represents the full cylinder length.

A common cylinder size on a standard uPVC door is 35/45 or 40/40, though doors vary considerably. Older timber frames, thicker composite doors, and doors with decorative handle furniture all change the numbers. Always measure your specific door rather than assuming a size. If you have a cylinder already removed, place it flat on a surface, find the centre cam (the small metal tooth in the middle that rotates when you turn the key), and measure from each end of the cylinder body to that cam. That gives you the same two figures. One important note: if your existing cylinder protrudes noticeably beyond the face of the door furniture on the outside, that overhang is a security problem — not just a sizing inconvenience — and we will come to that shortly.

Cylinder snapping is the most common method used by opportunistic burglars targeting uPVC and composite doors in London. The technique exploits a simple physical weakness: if the external portion of the euro cylinder sticks out beyond the door furniture by more than roughly 3 mm, it can be gripped with pliers or a mole wrench and snapped in two with a sharp rotational force. Once the outer section breaks away, the internal cam is exposed and the lock can be opened in seconds without a key. It is fast, almost silent, and requires no specialist knowledge — which is precisely why it became so widespread.

This is why correct measurement matters beyond just making the key turn smoothly. A cylinder that is 5 or 10 mm too long on the outside is not a minor inconvenience; it is a point of genuine vulnerability on an otherwise solid door. When you buy a replacement, look for cylinders rated to the TS007 3-star standard, or a combination of a 1-star cylinder with 2-star door furniture, which achieves the same overall rating. Anti-snap cylinders are designed to sacrifice the outer section in a controlled way, leaving the locking mechanism intact and the door secure. For anyone carrying out a door lock replacement London-wide — whether after a break-in attempt, a house move, or simply ageing hardware — specifying anti-snap as a minimum is sound advice. If you are unsure whether your current cylinder protrudes dangerously and you are in the Abbey Wood or Thamesmead area, our team can check it quickly. Call 020 3757 6072 — we are available around the clock.

Once you have your measurements, you are looking for a cylinder of the correct external and internal dimensions with security credentials that meet current standards. Beyond TS007, some cylinders also carry a Sold Secure Diamond rating and are listed in insurance-approved registers, which can matter when making a contents claim or when a letting agent specifies a minimum security level for a rented property. If you are a tenant in Abbey Wood, it is worth checking your tenancy agreement before changing any cylinder — in many cases you can arrange a lock change London with landlord permission and simply hand over a copy of the new key.

There are a number of situations where measuring up and replacing the cylinder is the right call. After a house move or the end of a tenancy, changing the lock means previous keyholders can no longer enter — the same outcome people often have in mind when they search for how to change a lock, though in the UK context a full cylinder swap is the standard approach rather than re-pinning. If you have lost a key, particularly a key that had your address attached to it, changing the cylinder promptly is the responsible step. If your key has become stiff, sticky, or intermittently fails to turn the cam, that is often a sign the cylinder is worn and operating outside its design tolerances. And if your door has had any kind of forced entry attempt — even an unsuccessful one — a professional inspection of the cylinder and frame should follow, because micro-fractures in the cylinder body are not always visible. For anyone needing upvc door lock repair London, the cylinder measurement process we have described is the same starting point a skilled locksmith will use on arrival.

Measuring a euro cylinder yourself is straightforward, and we encourage homeowners to do it — it means you can have an informed conversation about what parts are needed and why a particular size has been quoted. But fitting a cylinder correctly is a different matter. The retaining screw must be the right length for the new cylinder; the cam must align precisely with the multipoint mechanism; and the door furniture must sit flush so there is no external protrusion. A poorly fitted cylinder can leave the door impossible to lock from outside, or — worse — make it appear locked when it is not. For anything beyond the measurement stage, a professional fitting by an experienced locksmith London team is the reliable route.

Abbey Wood Locksmith operates as a 24 hour locksmith London service, covering SE2 and the surrounding areas including Thamesmead, Plumstead, Belvedere, and Erith. Whether you are locked out London and need immediate access, planning a door lock replacement London on a rented flat, or following up on a suspected snapping attempt, we send a locksmith straight away and are usually with you in around 30 minutes. The price for any job is confirmed upfront on the phone before anyone travels — the factors that shape the quote include the lock type, the parts required, the time of day, and travel distance. There are no hidden additions after the work is done. For a lock change London, an emergency locksmith London callout, or simply some advice on whether your cylinder size is a security risk, call 020 3757 6072 — we answer 24/7, including evenings, weekends, and bank holidays.

Our mobile team handles a wide range of locksmith work across London, including: euro cylinder measurement and replacement on uPVC and composite doors; anti-snap and TS007 3-star cylinder upgrades; multipoint lock mechanism repair and replacement; Yale-type nightlatch installation and replacement; 5-lever mortice deadlock supply and fitting; BS3621 insurance-approved lock upgrades; locked-out assistance for houses and flats; non-destructive entry for residential properties; door alignment and adjustment when a misaligned frame causes locking difficulties; uPVC door lock repair London covering gearbox, shootbolt, and hook-bolt faults; communal entrance door lock repair for blocks of flats; patio door and French door lock replacement; timber door lock upgrades; letter box replacement and security upgrades; door handle and escutcheon replacement; hinge bolt fitting for added door security; security survey and cylinder protrusion checks; post-break-in lock change London and door repair assessment; tenancy change-of-lock service with landlord liaison; lost key response and emergency cylinder replacement; lock-out response for ground floor and upper floor flats; door furniture alignment after warping or subsidence; deadlock and nightlatch combination fitting for insurer compliance; wooden door mortice lock upgrade to current British Standards; and 24 hour locksmith London emergency callout, every day of the year.

Euro cylinders are keyed mechanisms, but some homeowners and tenants also ask about how to change code on keypad door lock systems — typically digital locks fitted to communal entrances in blocks of flats or on rear garden doors. These operate differently from a cylinder: they use a PIN pad or electronic reader in place of a key, and changing the access code usually involves a short sequence entered on the keypad itself, following the specific instructions for that model. The same principle applies when people want to know how to change door lock code after a tenancy ends or following a security concern — the method depends entirely on the make and model of the digital lock. If you are unsure how yours works, or if the lock is unresponsive, a qualified locksmith can reset or replace it rather than risk a lockout caused by an incorrectly entered code sequence.