Euro cylinder measuring guide
Euro cylinders are measured from the centre of the fixing screw hole to each end of the cylinder. Record both sides separately, then choose the cylinder type and size that matches your door.
Open the door, undo the retaining screw on the edge of the door, turn the key slightly to line up the cam, then slide the cylinder out. Measuring the loose cylinder is usually more accurate than measuring it in the door.
Place the ruler on the centre of the fixing screw hole and measure to the end of the cylinder. This is one side of the size, often written as side A.
Keep the ruler on the centre of the screw hole and measure to the opposite end. This gives side B. The overall size should equal side A plus side B.
For offset cylinders, the two sides are different. Match the inside and outside before ordering, especially for thumbturn cylinders where the turn side must face indoors.
A 70mm cylinder could be 35/35, 30/40, or another split. Always record both sides.
Use the centre of the fixing screw hole as the reference point. The cam position can mislead the measurement.
If one side has a thumbturn, confirm which side faces inside before choosing the size.
Once you have the measurements, pick the matching cylinder style.
