How to Measure a Euro Cylinder

A euro cylinder is the barrel-shaped lock mechanism that slots into the central case of a multipoint locking system — the kind found on most modern uPVC front doors, composite doors, and many French or patio back doors. It is held in place by a single central screw and has a keyway on one or both ends. The cylinder is what your key actually turns, and it comes in a range of sizes measured in millimetres. Buy the wrong size and the cylinder will either not fit at all, or — far more dangerously — it will protrude beyond the door furniture, leaving it exposed to snapping attacks.

Across Leyton, Leytonstone, and the surrounding E10 and E11 postcodes, the vast majority of uPVC doors fitted in the last two decades use a euro cylinder. If your door has a handle in the middle and you lift it to engage the locking points before turning your key, you almost certainly have one. Knowing its exact size means any professional locksmith London-wide can order or bring the correct replacement cylinder — including a TS007 3-star anti-snap upgrade that your insurer may require.

Open your door so it is resting on the latch, giving you clear access to both faces. Look at the cylinder from the edge of the door — you will see a small screw in the centre of the door edge, usually on a metal plate called the faceplate or keeps plate. Undo that screw just far enough that it releases the cylinder's retaining cam, but do not remove it completely. You can now slide the cylinder out by inserting your key, turning it roughly 10 degrees, and pulling gently. Once it is in your hand, the measurement is straightforward: use a tape measure or a ruler to measure from the centre of the central screw hole to each end of the cylinder. Record both figures separately — the external measurement (outside the door, where the keyhole faces the street) and the internal measurement (inside your home). Write them as external x internal, so a cylinder measuring 35mm on the outside and 45mm on the inside is recorded as 35/45. The total length is 80mm.

If removing the cylinder feels uncertain — perhaps the door is stiff, the retaining screw is seized, or you live in a rented flat and your letting agent needs to be involved — you can get an approximate measurement without removing anything. With the door open, place your tape measure at the outer face of the door furniture (the external escutcheon plate) and measure to the centre of the door edge, then repeat from the internal face. These are not perfectly precise figures because the door furniture adds a small amount, but they are close enough to confirm the total cylinder length. The critical check at this stage is whether the cylinder sits flush with or slightly recessed into the door furniture on both sides. If any part of the barrel is visibly proud of the escutcheon plate, that is the snapping risk — and it needs to be addressed as a matter of urgency.

Cylinder snapping became widely reported in the UK around 2010 and remains one of the most common methods used to break into uPVC-door properties without leaving obvious signs of forced entry. The technique exploits a simple mechanical weakness: when a euro cylinder protrudes more than around 3mm beyond the door furniture, an intruder can grip it with mole grips or a similar tool and apply sideways force until the cylinder breaks at its weakest point — the anti-pick pins section. The outer part snaps off, leaving the inner section of the cylinder exposed. With the right implement, the door can be open in under a minute. No alarm is triggered, no glass is broken, and from the street it looks like someone is simply unlocking their own front door.

The fix is straightforward: fit a cylinder whose external measurement is correct for your door so it sits flush or just below the face of the escutcheon, and choose an anti-snap cylinder that meets the TS007 3-star standard. These cylinders are engineered with a sacrificial break point: if forced, they snap at a deliberately weak section at the front, but an internal steel clutch mechanism means the remaining stub cannot be used to operate the lock. Many home insurers now require a TS007 3-star or equivalent anti-snap cylinder as a condition of cover on uPVC doors, so it is worth checking your policy documents. If you are unsure whether your current cylinder meets that standard, an experienced locksmith London homeowners rely on can identify it at a glance — call 020 3757 6033 and we can advise before you book anything.

The most frequent error is measuring the total visible length of the cylinder without accounting for the door furniture. If your escutcheon plate sits proud of the door surface by 5mm on each side, your cylinder can appear to be 90mm when the actual cylinder you need is 80mm. Always measure to the outer face of the door furniture, not to the outer edge of the cylinder itself. The second common mistake is assuming both sides are equal. Many uPVC doors have an asymmetric cylinder — often 35mm outside and 45mm inside, or 40mm outside and 50mm inside — because the door panel itself is offset within the frame. A 45/45 cylinder installed in a door that needs a 35/45 will sit proud on the outside by 10mm, creating exactly the snapping vulnerability described above. If you are thinking about how to change a door lock or how to change a lock on a uPVC door, getting this measurement right before you buy anything is essential — the wrong cylinder wastes money and time.

A third mistake applies specifically to doors with a thumb-turn on the inside rather than a keyhole. These cylinders are measured the same way, but the internal end is longer to accommodate the thumb-turn mechanism, so the split is different. Never assume a like-for-like replacement is the same size as your existing cylinder just because it looks similar in a hardware shop. Bring the old cylinder with you, or better still, have a qualified locksmith carry out the door lock replacement London-wide so the correct part is sourced before the job begins. At Leyton Locksmith, we always measure on-site and confirm the specification before any cylinder is installed.

If you are already having the cylinder measured and replaced, it costs very little extra effort to step up to a higher-security option. The TS007 standard is a British kitemark specifically for euro cylinders and door hardware. A 3-star rating can be achieved with a single high-security cylinder, or a combination of a 1-star cylinder and 2-star door furniture. For most homes in Leyton and the surrounding area, a single TS007 3-star anti-snap cylinder is the most practical choice — it covers snapping, picking, drilling, and bumping in a single component. Look for cylinders that are also SS312 Diamond or Sold Secure Gold approved — both are independently tested to a rigorous standard and are widely accepted by UK insurers. If your door currently has a standard cylinder with no security grading marked on the box or body, there is a reasonable chance it offers minimal resistance to any of these attacks.

Beyond the cylinder itself, check that the retaining screw on the faceplate is in good condition. A loose or corroded retaining screw means the cylinder can be pulled without snapping — an even quicker method of entry. While you have the door apart, also inspect the multipoint lock mechanism: if the hooks or bolts feel sloppy, or the door drops on its hinges making it hard to lift the handle, a upvc door lock repair London specialist can usually adjust the hinges and reset the gearbox at the same visit. Getting all of this done together — cylinder upgrade, retaining screw, door alignment — means you are not leaving any single weak point for an opportunistic burglar to exploit. Our team covers emergency locksmith London call-outs across E10, E11, and the wider East London area every day of the year, including evenings, weekends, and bank holidays. For any door lock replacement London job or a straightforward cylinder upgrade, call us on 020 3757 6033 — we send a locksmith straight away and are usually with you in about 30 minutes.

Sometimes a measurement reveals that the cylinder is not just the wrong size — it is also worn out, damaged, or not up to current security standards. If your key is stiff to turn, the cylinder feels gritty, or it has been drilled or picked in a previous break-in attempt, a full lock change London job is the right course of action rather than a straight swap for a like-for-like replacement. Similarly, if you have recently moved into a rented property or purchased a home and do not know how many copies of the existing key are out there, changing the cylinder is far more reliable than worrying about who might have a spare. In the UK context the most common and practical approach is simply to fit a new cylinder. This gives you a fresh key set with no risk of an old copy being used.

For anyone locked out London-wide who has discovered mid-lockout that their cylinder is simply too worn to function, our 24 hour locksmith London service means you are never left waiting until morning. We carry a range of anti-snap cylinders in common sizes on the van, so in many cases the measurement, the replacement, and the security upgrade happen in a single visit. The price we charge is always confirmed with you on the phone before we set out — the final quote depends on factors including the lock type, the cylinder specification, the time of day, and travel distance. There are no hidden additions once the job is done.

Leyton has a particularly mixed housing stock. Victorian and Edwardian terraces on streets like Crownfield Road and Capworth Street often have timber front doors with a Yale-type nightlatch and a 5-lever mortice deadlock — these do not use euro cylinders at all and are measured and serviced differently. However, many of these same houses have had their back doors or side-access doors replaced with uPVC units over the years, and those will almost certainly have euro cylinders. Newer builds and converted flats throughout the E10 postcode, particularly around the Olympic Legacy development areas closer to Stratford, tend to have composite front doors with euro cylinders throughout. Knowing which type of door you have before you call or before you head to a hardware shop saves time for everyone. If you are not sure, a photo of the door edge and the lock mechanism sent to our number gives us enough to advise you over the phone.

Leyton Locksmith is a fully insured, mobile locksmith service operating across E10, E11, and the wider East London area. Our trained locksmiths handle the following: emergency door opening for locked-out residents, euro cylinder measurement and replacement, anti-snap cylinder upgrades to TS007 3-star standard, uPVC multipoint lock repair and replacement, composite door lock servicing, Yale nightlatch fitting and replacement, 5-lever mortice deadlock installation to BS3621, door alignment and hinge adjustment, door handle fitting and repair, letterbox replacement, timber door lock upgrades, communal entrance lock servicing for blocks of flats, landlord lock changes between tenancies, letting agent call-outs, housing association lock repairs, snap-and-entry damage repair, door frame reinforcement following forced entry, thumb-turn cylinder fitting, security assessments for uPVC and timber doors, uPVC door lock repair London across East London postcodes, 24 hour locksmith London emergency response, lock change London for new occupants, door lock replacement London for worn or damaged cylinders, anti-pick and anti-drill cylinder supply and fitting, locked out London assistance including overnight and weekend call-outs, and advice on upgrading to British Standard and Sold Secure Gold-rated hardware.