How to Measure a Euro Cylinder

A euro cylinder is the barrel-shaped lock insert found in the vast majority of uPVC and composite front doors fitted across Romford — from the terraced streets off London Road and the flat blocks near Romford Market to the newer-build semis out towards Collier Row and Harold Wood. It is the component that your key actually turns. Unlike a 5-lever mortice deadlock (which sits inside a wooden door and is opened with a larger, flat key) or a Yale-type nightlatch, the euro cylinder slides into a rectangular hole in the door and is held in place by a single central screw. That simplicity is both its strength and, if the cylinder is the wrong size or the wrong grade, its vulnerability.

When a cylinder extends too far beyond the door furniture — the metal rose or handle plate that frames it — a burglar can grip the exposed section with pliers, a mole wrench, or even a purpose-made snapping tool and snap the cylinder in two in a matter of seconds. The technique is known as lock snapping, and it has been recorded on streets across Havering and East London for years. A correctly sized, correctly specified cylinder removes most of that risk. Understanding how to measure yours is therefore not just a DIY curiosity — it is a genuinely useful piece of home security knowledge.

Remove the cylinder from the door before you measure — this gives you the most accurate result. To do this, open the door, locate the single screw on the edge of the door (the screw that passes through the door and into the centre of the cylinder), remove it, and then turn the key about 20–30 degrees to retract the cam (the small metal tongue inside) so the cylinder slides freely out of the lock case. Place the cylinder on a flat surface. You are going to take two measurements, both in millimetres. First, measure from the outer face (the face on the outside of the door) to the centre of the cylinder — this is the point where the screw hole sits. This is your external measurement. Second, measure from that same central screw hole to the inner face (the inside of the door). This is your internal measurement. A euro cylinder size is always written as external x internal, for example 35x45 or 40x40. Write both numbers down before you do anything else.

If you cannot or do not want to remove the cylinder, you can take an approximate measurement with the cylinder still fitted. Open the door, hold your tape measure against the outer edge of the door furniture (the escutcheon plate), and measure to the centre of the keyhole for the external figure. Then measure from the centre of the keyhole to the inner edge of the door furniture for the internal figure. Add 5mm to each reading to account for the furniture overlap, and you will be close enough to order the correct size. The golden rule is this: the cylinder should not protrude more than 3mm beyond the door furniture on the outside. If yours sticks out further than that, it is exposed to snapping and you should consider a replacement as a matter of priority. This is one of the most common findings our team makes when attending a door lock replacement Romford call-out — homeowners are often surprised to discover how much their cylinder sticks out.

Now that you have your measurements, you know the size — but size alone is not enough. The grade of cylinder matters enormously for a home in the Romford area. Standard euro cylinders, the type often installed by builders on new-build properties, offer very limited resistance to snapping. If your insurer asks about lock standards (many do, particularly for contents cover), or if you simply want to know your front door is doing its job, look for a cylinder that carries the TS007 3-star rating or a Sold Secure Diamond rating. These cylinders are designed with a deliberate sacrificial section that breaks harmlessly before the lock mechanism is compromised, combined with anti-pick and anti-drill features. When you are discussing a lock change Romford with our team, we will always advise on the appropriate grade for your specific door type and situation — there is no one-size-fits-all answer, and the right choice depends on your door construction, your existing handle furniture, and the level of security you need.

One important point: the replacement cylinder must match your measured size, or be within 5mm on each side, to fit correctly. Going too long on the external side re-introduces the snapping risk. Going too short means the cylinder may not engage the cam properly, leaving the lock inoperable. If you are unsure, our experienced locksmiths carry a range of sizes and grades and will confirm the correct fit on-site before the work begins.

Measuring the euro cylinder is straightforward when the lock is functioning and the door is opening. It becomes a different matter when the cylinder has already been snapped, the door will not open from either side, or the multi-point locking mechanism on a uPVC door has failed and the handle drops or stiffens. In those situations — which represent a significant proportion of our upvc door lock repair Romford calls — you need a locksmith on-site rather than a tape measure. A snapped or jammed cylinder can sometimes be extracted non-destructively by a skilled technician; in other cases the door needs to be opened using controlled techniques that avoid damage to the door frame, and the lock is then replaced from scratch. How much any of this costs depends on factors including the type of door, the extent of the damage, the time of day (evenings, weekends, and bank holidays affect the final quote), travel distance, and the parts needed. We always confirm an exact price before any work begins — there are no surprises on the invoice.

If you are locked out right now, the first thing to do is check every other potential entry point: back doors, ground-floor windows, and whether a trusted neighbour or family member holds a spare key. If none of those options are available, call us. As a 24 hour locksmith Romford residents rely on day and night, we send a locksmith straight away and are usually with you in about 30 minutes. Call 020 3757 6539 — we answer every call, any hour.

Once you have the right cylinder fitted at the right size, a few straightforward habits will extend its life and keep it performing reliably. Spray the keyway lightly with a dry graphite lubricant or a dedicated lock lubricant two or three times a year — avoid WD-40 inside the keyway as it attracts dust and can gum up the pins over time. If your uPVC door has dropped slightly on its hinges (a common occurrence in Romford's older housing stock where ground movement is not unusual), the cylinder can start to bind as the door and lock case fall slightly out of alignment. The fix is usually a hinge adjustment, not a new cylinder, though a stiff or grinding action in the lock is always worth getting checked before it becomes a full failure. Keep an eye on the amount of cylinder that sits proud of the door furniture — if you have ever swapped handle sets or had work done on the door, it is worth re-checking that measurement to make sure nothing has changed.

Knowing how to change a lock or swap a cylinder yourself is a useful skill, and this guide gives you the foundation. That said, if you discover that your cylinder is damaged, the door alignment is off, or you simply want the peace of mind that the job has been done correctly, our team at Romford Town Locksmith is available every day of the year. We cover Romford town centre, Collier Row, Gidea Park, Harold Wood, Harold Hill, Hornchurch, Elm Park, and surrounding areas in the RM postcode districts — and we keep detailed notes on the door types and lock sizes common to this patch so we always arrive prepared.

[11] We handle a wide range of residential and commercial locksmith work across the Romford area. Our services include: euro cylinder replacement, anti-snap cylinder upgrades, TS007 3-star cylinder installation, uPVC door lock repair, composite door lock repair, wooden door lock repair, 5-lever mortice deadlock installation, Yale nightlatch replacement, multipoint lock repair, multipoint lock replacement, door panel lock repair, emergency lockout response, non-destructive entry, controlled forced entry when necessary, door alignment checks and adjustments, hinge adjustment and replacement, letterbox security upgrades, door handle and escutcheon replacement, cylinder changes and re-pinning, security surveys and lock upgrade advice, landlord and letting agent lock changes between tenancies, lock changes following a lost or stolen key, lock changes following a suspected break-in or attempted entry, boarding up following a break-in (temporary security), communal entrance lock repair for blocks of flats, and general door security consultations. If you are unsure whether your situation falls within our services, just call 020 3757 6539 and we will tell you plainly what we can do and what it will involve before anyone travels out to you.