How to Measure a Euro Cylinder

A euro cylinder is the oval-shaped barrel that sits in the centre of most uPVC and composite front doors, as well as many back doors and French doors across Lewisham and the wider south-east London area. It is the part your key actually enters. The cylinder is held in place by a single central screw, and that simplicity is both its strength and its vulnerability. If the cylinder protrudes beyond the door handle or escutcheon plate — even by five millimetres — an opportunist can grab that exposed section with a tool and snap the cylinder in two. Once snapped, the door opens in seconds without a key. Anti-snap euro cylinders are designed with a deliberate break point that sacrifices the outer section while protecting the inner cam that controls the lock bolt. This is why the measurement is not just a matter of making the cylinder fit: it is a matter of making sure nothing extends beyond the door furniture for someone outside to grip.

Lock snapping has been a recognised method of break-in across London for well over a decade. Streets around Lewisham station, the flats along Loampit Vale, and the semi-detached houses running towards Catford are all typical uPVC-door territory where this risk is real. Knowing your cylinder size means you can specify a correctly sized anti-snap replacement — one that sits flush or fractionally recessed — rather than simply picking the nearest cylinder off a shelf and hoping it fits.

You need a metal ruler or a tape measure — a flexible cloth tape is less accurate for this job, so a rigid steel rule is better. Remove the single central screw on the interior face of the door (a standard Phillips head), slide the cylinder out, and lay it on a flat surface. You will immediately see that it is not symmetrical. One side is longer than the other: the longer side goes to the outside of the door and the shorter side sits on the inside. Measure from the centre of the central fixing hole to each end of the cylinder separately, then note both figures. Euro cylinders are sold as, for example, 35/45, meaning 35mm on the inside and 45mm on the outside. The total length in that case is 80mm. Always confirm the total length as a final check — if your two individual measurements add up correctly to your total, your figures are right.

If you cannot or would rather not remove the cylinder first, you can measure it in situ. Open the door so you can access both faces. Hold your ruler flat against the door face on the outside and measure from the outer edge of the cylinder to the centre of the fixing screw. Repeat on the inside. You will not get quite as clean a reading as you would on a workbench, but it is usually accurate enough to order the right size. The critical point is to also note how far the cylinder currently sits relative to the door furniture: if it is already proud of the handle rose or escutcheon, you have identified a snapping risk that needs addressing when you change the lock. A correctly fitted replacement should sit flush or sit at most a millimetre or two recessed. Never go larger on the external measurement than is needed to reach flush — every extra millimetre is a potential grip point.

The single most common mistake is buying a cylinder based only on total length without noting which side is which. A 35/45 cylinder and a 45/35 cylinder are the same total length but are mirror images of each other. Fit one the wrong way round and either the key will not reach, or — far more seriously — the longer section ends up on the inside, making the external face even shorter and potentially unable to reach the door furniture at all. Always note which measurement belongs to which face before you remove the old cylinder, or take a photograph of it in situ first.

The second mistake is buying a standard cylinder when a TS007 3-star anti-snap, anti-pick, anti-drill cylinder is what the door actually needs. Many home insurance policies in the UK now specify a minimum security standard for door locks — sometimes asking for BS3621 compliance or a specific star rating — and fitting the wrong type could affect a claim. If you are a tenant, check with your letting agent or managing agent before changing anything: they may require a specific product or may need to supply a replacement key. If you are unsure which cylinder your door needs, or if the door has been damaged and you are locked out, the fastest and safest route is to call a trained locksmith rather than force the issue. Our team covers Lewisham and the surrounding SE postcodes around the clock — call 020 3757 5731 and we will confirm an exact up-front price before anyone sets off.

There are situations where measuring is a step you have already missed. If your key has snapped in the cylinder, if the cylinder itself has been attacked and snapped by an intruder, or if you are simply locked out London with no spare key to hand, the priority is regaining access safely — not running a ruler over anything. In those circumstances, a trained 24 hour locksmith London can open the door non-destructively in most cases, or fit a correctly sized replacement cylinder on the same visit. We carry a range of anti-snap cylinders in common sizes so that door lock replacement London can usually happen in a single call-out rather than requiring a return visit once parts arrive.

One scenario worth knowing about specifically: if your uPVC door has dropped on its hinges — common in older frames across the terraced and semi-detached housing stock in SE13 and SE6 — the cylinder may appear to be faulty when the real problem is door alignment. A dropped door puts the multipoint lock mechanism under strain, and no amount of cylinder replacement will fix that until the alignment is corrected. This is an area where an experienced locksmith will diagnose the actual cause rather than simply swapping parts. UPVC door lock repair London is often as much about the door as the lock, and getting that diagnosis right on the first visit saves time and money.

Once you have your measurements, you are in a position to specify a replacement with confidence. Look for cylinders that carry a TS007 3-star rating, or a combination of a 1-star cylinder and a 2-star door handle that together achieve 3 stars — both configurations meet the same standard. The 3-star rating covers snapping resistance, picking resistance, and drilling resistance. Some cylinders also carry Sold Secure Diamond or British Kite Mark accreditation, which certain insurers ask for by name. When you change a door lock or change a lock on a uPVC door to a 3-star product, you are not just replacing a worn part — you are actively improving the security of the door in a measurable way.

If you would like a professional to handle the measurement, supply the cylinder, and carry out the fitting, our team can do all three on a single visit. The final price depends on factors including the type of door and frame, the cylinder specification you need, the time of day, and travel to your address — but we confirm an exact figure before any work begins. There is no guesswork and no bill that surprises you after the job. For a lock change London on a standard uPVC front door, the visit typically takes under an hour from arrival to handing over the new keys. We work across Lewisham, Hither Green, Catford, Lee, Brockley, and the surrounding SE postcode districts. Call us on 020 3757 5731 — we answer 24 hours a day, every day including evenings, weekends and bank holidays.

Here is a full picture of what our mobile team can help with across the Lewisham area and greater south-east London: emergency lockout assistance for houses and flats; non-destructive entry on uPVC, composite, and timber doors; euro cylinder measurement and replacement; anti-snap TS007 3-star cylinder upgrades; 5-lever mortice deadlock supply and fitting; Yale-type nightlatch replacement; multipoint lock mechanism repair and replacement; uPVC door lock repair including dropped-door alignment assessment; uPVC door handle and gearbox replacement; composite door lock replacement; communal entrance door lock repair for blocks of flats; deadlock fitting to meet BS3621 insurance requirements; lock change following a tenancy change or lost key; lock change following a burglary or attempted break-in; emergency boarding-up after a forced entry; damaged door frame repair and reinforcement; door hinge replacement and adjustment; letter box security upgrades including anti-snap letter box covers; door chain and door bar fitting; nightlatch supplementary fitting to timber doors; patio door lock repair and cylinder replacement; French door multipoint lock repair; internal door lock fitting; lock inspection and security survey for Lewisham homes; and 24-hour emergency response seven days a week including bank holidays. Every job is carried out by an insured, experienced locksmith and priced transparently before we begin.

If you are locked out of your home in Lewisham or anywhere across south-east London, run through these checks first — not because we mind the call, but because they can save you waiting time. Check all other entry points: a back door, a bathroom window on a low level, or a garden gate that might still be unlocked. Contact anyone else who holds a spare key — a family member, a neighbour, your letting agent if you rent the property. If you are a tenant and cannot reach your letting agent, check your tenancy agreement for the emergency contact procedure; some managing agents have an out-of-hours line. If none of that works, call a locksmith. Do not attempt to force the door, use a credit card on a mortice deadlock, or follow advice found online about how to pick a door knob lock — these approaches either damage the door or simply do not work on modern locks, and in the case of a rented property they may put you in breach of your tenancy.

When you do call us, have your address and postcode district ready, and if possible describe the type of door — uPVC, composite, or timber — and whether you can see a Yale latch, a mortice deadlock, or a multipoint mechanism on the edge of the door. That information lets us send the right locksmith with the right parts straight away. We are usually with you in about 30 minutes, though travel time varies with traffic and location. We will confirm the exact price on the phone before anyone sets off — there are no surprises on arrival.