How to Measure a Euro Cylinder

A euro cylinder — sometimes called a euro profile cylinder — is the barrel-shaped locking mechanism fitted inside most uPVC and composite front doors across the UK. It is the component that your key actually turns. You will recognise it by the oval or oblong metal faceplate visible on the door edge, with a keyhole on the outside and, on most models, a turn-knob or thumbturn on the inside. If your door is a uPVC door with a multipoint locking system — the kind where the handle lifts up and engages several locking points at once — it almost certainly uses a euro cylinder.

Euro cylinders are also common on composite doors fitted in purpose-built blocks of flats, terraced houses along Stroud Green Road, and newer-build properties around the Finsbury Park area. Older Victorian and Edwardian properties in N4 are more likely to have a Yale-type nightlatch on the top and a 5-lever mortice deadlock lower down, but even some of those have had uPVC rear doors or communal entrance doors added over the years, so it is worth checking every external door in the property.

You will need a tape measure or a small ruler. Open your front door and look at the edge — the narrow face of the door you see when it is open. You will see the cylinder faceplate, usually held in by a single screw in the centre. The measurement you need is the total length of the cylinder, split into two halves: the external (outside) measurement and the internal (inside) measurement, with the centre screw hole as your reference point. Measure from the outside edge of the cylinder to the centre of the fixing screw, then measure from the centre of the fixing screw to the inside edge. Write both numbers down. A typical result for a standard uPVC front door might be 35mm on the outside and 35mm on the inside, written as 35/35. Other common sizes are 35/45, 40/40, or 45/45, but doors vary considerably, so always measure your specific door rather than guessing.

If you cannot easily access the cylinder faceplate — for instance if the door is not opening properly or the existing cylinder is damaged — you can remove the cylinder itself first. Unlock the door, open it, locate the central retaining screw on the door edge, unscrew it, insert your key and turn it slightly to retract the cam, then slide the cylinder out. Lay it on a flat surface and measure the total length, then identify the fixing-hole centre point, which is usually marked by a small notch or the cam slot. If the numbers are not clean multiples of five, round up to the nearest 5mm — cylinders are manufactured in 5mm increments. Take a note of the brand stamped on the cylinder if you can see it, but do not worry if the brand is unfamiliar — what matters for ordering or for your locksmith to match is the size and the security standard, not the brand name.

Here is the detail that most DIY guides skip over. If the outer portion of your euro cylinder extends more than a few millimetres beyond the surface of the door, it creates a grip point that a burglar can use with a pair of snap pliers or similar tools. The technique, known as cylinder snapping, takes seconds and bypasses the entire multipoint lock system regardless of how many locking points are engaged. It is the most common method used to break into uPVC doors in London and has been well-documented by police forces across the country for well over a decade.

The fix has two parts. First, the cylinder should sit flush with the door furniture — the external measurement should ideally be no more than 3mm proud of the escutcheon plate (the decorative surround). If your current cylinder protrudes significantly, that alone is a reason to arrange a door lock replacement London. Second, the cylinder itself should carry the TS007 3-star rating, or a combination of a 1-star cylinder with 2-star door furniture that together achieves 3-star protection. These cylinders are engineered to resist snapping, drilling, picking, and bumping. Many home insurers now ask for anti-snap cylinders as a condition of cover, particularly for policies on properties in London, so fitting one is not just a security upgrade — it can also keep your insurance valid. If you are unsure whether your current cylinder is anti-snap rated, a quick call to our team on 020 7871 7826 will get you a straight answer — we can usually assess a cylinder from a photograph sent by message.

Measuring your cylinder is only step one. Once you have the numbers, you need to decide whether you are replacing a like-for-like cylinder, upgrading to an anti-snap model, or whether the door itself has an underlying problem that a new cylinder alone will not solve. A lock change London job is straightforward when the door and frame are in good condition and the cylinder is simply worn or the wrong security grade. It becomes more involved when the door has dropped on its hinges (causing the cylinder to bind), when the multipoint mechanism itself has failed, or when a previous forced entry has damaged the door frame.

There are some situations where it is genuinely worth calling a professional before you order parts. If you have recently moved into a flat or house in Finsbury Park — particularly a rental where the letting agent handed over keys that may have been copied multiple times — changing the cylinder promptly is sensible practice. The same applies after a break-in, a lost key, or a relationship breakdown where someone else holds a key to your home. Our team handles lock change London work every day across N4, N7, N5, and the surrounding postcodes, and we carry a range of TS007-rated cylinders in the van so the work can usually be completed in a single visit without you having to source parts separately. If you would like us to assess your door and confirm an exact up-front quote before any work begins, call 020 7871 7826 — we answer around the clock.

If the reason you are reading this is that your door will not open right now — the key will not turn, the handle will not lift, or the lock has seized — then measuring the cylinder is a secondary concern. The priority is getting back inside safely. Before calling anyone, run through the basics: is there a back door or a ground-floor window that is accessible and unlocked? Does a neighbour, family member, or your letting agent hold a spare key? If you are in a block of flats, is the problem with your own front door or the communal entrance? For upvc door lock repair London scenarios, the fault is often not the cylinder itself but the multipoint mechanism — a snapped gearbox, a dropped door, or a cam that has become misaligned. These require a different approach than a simple cylinder swap.

What we would never advise is attempting to force, drill, or bypass a lock yourself unless you own the property outright and have exhausted every legitimate alternative, and even then the risk of causing expensive door damage is high. For locked out London situations, our team operates as a 24 hour locksmith London service — we send a locksmith straight away and are usually with you in around 30 minutes. We will confirm the cause of the problem before doing any work, explain your options clearly, and give you an exact price to agree before we start. The final cost of an emergency locksmith London call-out depends on factors including the type of lock involved, the time of day or night, travel distance, and whether parts are needed — there are no hidden additions once you have agreed the quote on the phone.

Once you have your measurement — say 35/45 — and you know the door is in good condition, you are ready to choose a replacement. For most uPVC and composite front doors in this part of North London, the recommendation is a TS007 3-star anti-snap cylinder in the correct size. These are available at a range of price points from reputable hardware brands, and the quality difference between a budget cylinder and a properly rated one is significant. Look for cylinders that are explicitly marked as anti-snap, anti-drill, anti-pick, and anti-bump — a good 3-star cylinder should resist all four attack methods.

One practical note for anyone in a rented property or a leasehold flat: check with your landlord or the managing agent before changing the cylinder, as some tenancy agreements and leasehold documents require the freeholder's consent or stipulate that only an approved contractor carries out the work. If you are a landlord yourself and need a lock change across multiple properties, or a letting agent dealing with an urgent situation after a tenant has moved out, we work with both on a regular basis across the Finsbury Park area. For any cylinder question — sizing, security rating, or whether your door is vulnerable to snapping — call 020 7871 7826 and we will give you a straight, honest answer with no obligation.