Measure and Identify a Euro/DIN Cylinder

A Euro/DIN profile is a useful starting point, but it does not prove that a smart lock will fit or operate the door. Record the cylinder on both sides, how the lock normally moves, and the clearances and cylinder function required by the exact product and market version.

Schematic only. Use the reference points and limits in the exact product guide; this drawing is not to scale.

Identify the cylinder and its controls

Look at the cylinder from both sides of the door and note its profile, any visible markings, and whether the inside control is a key or a thumbturn. Also record the door furniture around it and whether a separate latch or multipoint lock is present. A matching profile name does not identify the lock case, cam, cylinder length, or full door sequence.

Measure each side on its own

Use the measurement reference specified by the candidate smart-lock or replacement-cylinder guide. Record the inner and outer lengths separately, along with the stated starting point, the door-plate or furniture reference, and how far either end projects beyond the fitting. Do not combine a measurement that includes furniture with one that excludes it. Projection and the product’s measured cylinder length can be different checks.

Nuki’s Smart Lock Ultra guide, for example, measures from the retaining screw to each door plate and excludes cylinder overhang. For this named model, the guide lists Euro-profile cylinders, a maximum inside length of 68 mm and outside length of 55 mm, with extensions available above the outside limit. It also gives swing-specific frame and handle clearance thresholds. Those are Smart Lock Ultra screening values, not Euro/DIN standards or limits for another Nuki version.

• For an inward-opening door, the guide asks for more than 30 mm from the keyhole center to both the frame and handle.
• For an outward-opening door, it asks for more than 40 mm to the frame and more than 30 mm to the handle.

A dimensional pass answers only the measurements named by that product guide; the other required checks remain separate.

Check the action as well as the dimensions

With the door open, use the key or thumbturn normally and note whether it moves a deadbolt, retracts a latch, or depends on a handle lift. Do not force the key or handle. Check any emergency-key requirement with the exact cylinder and product instructions; the emergency-function guide explains why a function name alone is not enough.

Compare the complete record with the exact smart-lock guide, including market, inside control, dimensions, clearances, emergency function, and required lock action. If one of those details is missing or the door’s sequence is unclear, leave the result unverified and ask the manufacturer or a qualified locksmith. Use the regional profile guide and compatibility checklist to carry the remaining details forward.