How to Measure a Euro Cylinder

A euro cylinder is the barrel-shaped lock insert fitted to most uPVC and composite front doors across London. It is the component your key turns, and it sits inside a rectangular metal housing in the door. Euro cylinders come in a huge range of sizes — from around 70 mm total length up to 110 mm or more — and fitting even a few millimetres too long on the outside of the door is enough to make the lock vulnerable to a technique called cylinder snapping, where a burglar uses leverage to shear the cylinder in half and gain entry in seconds. Getting the measurement right is therefore not just about convenience; it is a direct security decision.

The two numbers that define a euro cylinder are the external measurement (from the outer face of the door to the centre of the fixing screw hole) and the internal measurement (from that same screw hole to the inner face of the door). These are usually written as, for example, 35/45 — meaning 35 mm on the outside and 45 mm on the inside. The total length of the cylinder is the sum of both figures. If you currently have a cylinder that is too long on the outside, changing it to the correct size — or switching to an anti-snap, TS007 3-star rated cylinder — is one of the most effective lock change London homeowners can make.

You will need a tape measure or a steel rule, and ideally a pen and paper. Start by opening the door so you can work on it comfortably. Look at the edge of the door — you will see a small screw going horizontally through the edge of the door into the lock body. That screw holds the cylinder in place. The centre of that screw hole is your reference point for both measurements. First, measure from the outer face of the door (the side that faces the street) to the centre of the fixing screw hole. Write that number down — this is your external dimension. Next, measure from the centre of the same screw hole to the inner face of the door (the side that faces your hallway). Write that down — this is your internal dimension. Add both together for the total cylinder length. So if the outside measures 35 mm and the inside measures 45 mm, you need a 35/45 cylinder, which is 80 mm in total.

A few things to watch for. If your door has a handle that sits on a backplate rather than a rose, make sure you measure to the actual door face, not to the edge of the handle furniture. On some older timber doors in Fulham's Victorian and Edwardian terraces, the door itself can be quite thick, so double-check by measuring twice. If the existing cylinder protrudes more than 3 mm beyond the outer face of the door, that is a snapping risk — many experienced locksmiths recommend fitting a cylinder where the external portion is as short as the door furniture allows, combined with a sacrificial or anti-snap design. If you are unsure about any part of the measurement or which cylinder grade is right for your door, a qualified locksmith can assess it quickly during a door lock replacement London visit.

Cylinder snapping became a widely recognised problem across London and other UK cities as uPVC doors became the standard on new builds and replacement front doors. The attack is straightforward in concept: if enough of the cylinder sticks out beyond the door face, a burglar can grip it with mole grips or snap it using a screwdriver and a sharp downward kick. The outer portion breaks away, and the remaining inner stub can be turned with a flathead screwdriver, opening the door within moments. It is not a skilled technique, which is precisely what makes it dangerous — it requires no specialist knowledge, leaves relatively little noise, and can be completed before a neighbour on the pavement opposite has time to react.

The fix is equally straightforward. First, fit a cylinder whose external portion does not protrude unnecessarily — flush or just slightly recessed is ideal. Second, choose a cylinder rated to TS007 3-star or at least one that carries a British Standard anti-snap designation. These cylinders are engineered with a sacrificial section that breaks at a point that does not expose the locking mechanism. Third, if your door is fitted with a standard thumb-turn on the inside, consider whether a key-operated interior is more appropriate for a ground-floor flat or a door with glazing nearby. If you have been meaning to look into how to change a lock or upgrade your cylinder and have kept putting it off, the snapping risk is a good reason to move it up the list. Our team offers upvc door lock repair London and full cylinder replacement across Fulham and the surrounding area — call 020 7871 7823 and we will advise you on the right grade of cylinder for your specific door before anyone comes out.

Once you have your measurement, you need to decide on the cylinder specification. At the basic end, standard euro cylinders offer very little resistance to snapping or picking. A step up is an anti-snap cylinder, which includes a break point engineered away from the locking pins. Better still is a TS007 3-star rated cylinder, which meets a British Standard for resistance to snapping, picking, drilling and bumping — insurers and local authority housing teams increasingly specify these on new and replacement doors. If your insurer requires BS3621 compliance on your locks, check whether the cylinder you choose is compatible with that standard, as some composite and uPVC multipoint lock systems have specific requirements. It is worth asking your locksmith to confirm compatibility before the cylinder is ordered.

You may also come across cylinders described as anti-pick, anti-drill, or anti-bump. Each term refers to a specific attack method and a specific design feature inside the cylinder. A good quality 3-star cylinder will usually address all of these, but it is worth confirming rather than assuming. For landlords managing properties in Fulham — particularly houses in multiple occupation around Munster Road or flats in the North End Road area — keeping records of which cylinder grade is fitted and when it was last changed is good practice and may be relevant to insurance and tenancy obligations. If you need a lock change London with a verifiable upgrade in security grade, our experienced team can supply and fit the correct cylinder and confirm the specification in writing.

Measuring and swapping a euro cylinder is well within the ability of a confident DIYer on a standard uPVC door, provided the existing cylinder comes out cleanly and the replacement fits without forcing. However, there are several situations where calling a skilled locksmith is the right move. If the existing cylinder has been snapped, damaged or tampered with, the internal mechanism may be compromised in ways that are not obvious from the outside, and forcing a new cylinder in without checking can damage the multipoint lock body — an expensive component to replace. If you are locked out London and cannot get in, do not attempt to force anything; check for a spare key with a trusted neighbour, verify whether a back door or ground-floor window is accessible with permission, and if not, call a professional. For anyone wondering how to change a door lock on a uPVC door for the first time, it is worth watching a reputable guide for your specific door brand first, and if there is any doubt, the cost of a locksmith call-out is far less than the cost of a damaged door frame or a lock body that needs replacing.

Our team operates as an emergency locksmith London service around the clock — evenings, weekends and bank holidays included. We work across Fulham, covering SW6 and the surrounding postcodes, and we send a locksmith straight away when you call; we are usually with you in about 30 minutes. The price for any job is confirmed clearly on the phone before anyone leaves — there are no surprise figures on arrival. Factors that affect the final quote include the type of lock, the cylinder specification needed, the time of day and the parts required. Call us on 020 7871 7823 whenever you need us — we answer 24/7 as your 24 hour locksmith London.

As a fully insured, mobile locksmith team serving Fulham and the wider south-west London area, we handle a wide range of residential and commercial lock work. Our services include: euro cylinder replacement; anti-snap cylinder upgrades; TS007 3-star cylinder supply and fitting; uPVC multipoint lock repair; uPVC multipoint lock replacement; Yale nightlatch fitting; Yale nightlatch repair; 5-lever mortice deadlock fitting; BS3621 mortice deadlock replacement; composite door lock repair; timber door lock repair; door lock replacement London-wide; emergency locksmith London call-outs; locked-out London response; communal entrance lock replacement; deadlock fitting to rear doors; deadlock fitting to side-access doors; lock change London after a break-in; lock change following a lost key; damaged cylinder replacement; lock change after a tenancy change; landlord lock-change service; letting agent emergency response; housing association lock repair; door frame repair after forced entry; and security assessments for residential properties. If your specific need is not listed, call 020 7871 7823 and we will tell you straightforwardly whether we can help.

When you need lock work done — whether it is a planned cylinder upgrade or an unexpected lockout — it pays to know who you are dealing with before you open the door. In London, as in any large city, the range of people offering locksmith services is wide. Some questions worth asking: are they insured? Can they confirm the job price before they arrive? Do they carry the cylinder specification you need, or will they fit whatever they have in the van? Our team is fully insured, trained and experienced specifically in the locks fitted to the doors found across Fulham — the Victorian terraces off Fulham Broadway, the purpose-built blocks near the Riverside, the newer composite-door developments along the river towards Putney. We do not subcontract, we do not operate a referral model, and we do not charge you to find someone else. When you call 020 7871 7823, you speak directly to us, and we tell you honestly whether we can help and what it will cost before we set off.