How to Measure a Euro Cylinder

A euro cylinder is the oval or rectangular barrel that slots into a uPVC, composite, or aluminium door and is held in place by a single central screw. Turn the key and it drives the multipoint locking mechanism up and down the door slab. They are found on the vast majority of modern front and back doors fitted in the UK over the past two decades, including most uPVC patio doors and French doors. If your door has a lever handle rather than a traditional round knob, the chances are high that it uses a euro cylinder.

The size of a euro cylinder is expressed as two numbers separated by a slash — for example, 35/45 or 40/40. The first number is the distance from the centre of the fixing hole (where that retaining screw sits) to the external face of the cylinder, and the second number is the distance from the centre of the fixing hole to the internal face. Add them together and you get the total length. A 35/45 cylinder, for instance, is 80 mm in total. Getting these measurements right is not just about fitting; it is a direct security issue. A cylinder that is too long protrudes past the door furniture and can be gripped and snapped. A cylinder that is too short may not engage the cam properly, leaving the lock unreliable. Neither situation is acceptable on a front door you rely on every day.

You will need a tape measure or a steel rule — a fabric tape can flex and give you a slightly false reading, so a rigid rule is better. Open your door so you can access both sides comfortably. First, locate the central fixing screw on the edge of the door and use a screwdriver to back it out a few turns (you do not need to remove it fully). This releases the cylinder so you can study it in situ, though you do not need to pull it out to take your measurements. Close the door again once you are ready to measure.

On the outside face of the door, measure from the outer edge of the cylinder barrel to the centre of the fixing hole. Write that number down — this is your external measurement. Then go to the inside of the door and measure from the inner edge of the cylinder barrel to the centre of the same fixing hole. Write that number down — this is your internal measurement. So if the outside reads 40 mm and the inside reads 45 mm, your cylinder is a 40/45. Now comes the critical check: compare both measurements to the edge of your door furniture (the decorative plate or handle rose that surrounds the cylinder on each face). If the cylinder sits flush with or slightly recessed behind the furniture, it is correctly sized. If it protrudes beyond the furniture, even by 3 or 4 mm, it is a snapping risk and should be replaced. As a locksmith Croydon residents call day and night, we see protruding cylinders on doors across CR0, CR2, and CR7 more often than we would like — it is a genuinely widespread issue in housing built between the late 1990s and early 2010s.

Standard euro cylinders are made with a deliberate weak point roughly at the centre, partly as a consequence of their internal engineering. When a cylinder protrudes, a would-be intruder can grip that exposed section and apply rotational and lateral force simultaneously. The cylinder breaks at that weak point, the cam is released, and the door opens — often in under thirty seconds. This technique requires no specialist skill, no lock-picking ability, and leaves very little noise or evidence. It has been a documented problem in the UK for well over a decade and contributed directly to the development of anti-snap, anti-drill, and anti-pick cylinders rated to TS007.

The solution is straightforward: fit a correctly sized cylinder that sits flush, and choose one rated to at least TS007 1-star or, ideally, TS007 3-star (which combines the cylinder and handle ratings). Many home insurers now ask specifically whether your uPVC door has an anti-snap cylinder, and some policies include it as a condition of cover. If you are a tenant, your landlord or letting agent has an obligation to maintain secure entry points, so it is worth raising the issue in writing if you spot a protruding cylinder. If you need a door lock replacement Croydon side done properly and promptly, our experienced team carries a range of TS007-rated cylinders and can advise on the right grade for your specific door. Call 020 4542 3118 and we will confirm an exact up-front price before any work begins.

The most frequent error is measuring the cylinder after it has already been removed and placed on a worktop. Without the door as a reference point, it is easy to measure to the wrong landmark — particularly if the cylinder has a thumb-turn on one end, which adds length but is not part of the cam-to-face measurement. Always measure in situ with the cylinder in the door, or, if the cylinder has already been removed, measure to the centre of the cam (the small protruding lug at the middle) rather than to the fixing-hole opening. A second common mistake is ignoring the thickness of any existing escutcheon plate or cylinder pull handle. If you are replacing a plain cylinder with one that includes an external pull, the pull adds a few millimetres to the effective external length — your locksmith can account for this, but it is worth flagging when you order.

A third issue arises on older timber doors that have been fitted with a euro cylinder lock as an upgrade. Timber doors are often thicker than standard uPVC slabs, and the cylinder fixings may have been shimmed or packed out. In this case, measuring from the centre of the fixing hole remains correct, but the total length you need will be longer than typical uPVC sizes. If anything is unclear after you have taken your measurements, bring the figures (and ideally a photo of the door edge) when you contact a locksmith. As an emergency locksmith Croydon residents rely on at all hours, we are happy to talk through measurements over the phone before you commit to anything.

Sometimes measuring a cylinder reveals not just a sizing problem but a lock that is already damaged — a barrel that spins freely, a cam that is cracked, or a housing that has visible signs of attempted forced entry. In those cases, a simple cylinder swap is the right move; in others, you may need a broader upvc door lock repair Croydon service that addresses the multipoint mechanism behind the cylinder, the keep (the metal plate on the door frame that the hooks and bolts engage with), or the door alignment itself. A door that has dropped slightly on its hinges, for example, will put the lock under constant stress and wear the cylinder far faster than normal.

Our 24 hour locksmith Croydon service covers all of this: emergency lockouts across the borough, cylinder replacements, multipoint lock repairs, and security upgrades on timber, uPVC, and composite doors. We work across Croydon town centre and throughout the surrounding areas — from the streets around Addiscombe tram stop to South Norwood, Thornton Heath, Purley, and beyond. When you call 020 4542 3118, we send a locksmith straight away and are usually with you in about 30 minutes. We will confirm an exact price on the phone before we set out — the final quote depends on the lock type, any parts required, and the time of day — so there are no surprises on the doorstep. If you have spotted a protruding cylinder, a stiff key, or any sign that your door lock is not performing as it should, that is the right moment to act, not after a problem occurs.