How to measure Euro-cylinder locks, to get the right fit
Changing your locks to improve home security is an easy way to beat the criminals at their own game, some of the easiest to refit are Euro-cylinder locks, which are widely used in uPVC doors found in most modern homes.
One of the most important things to consider when you replace a euro-cylinder lock is the length, making sure you have the correct fit will improve your door security and make the job easy.
Get this wrong and it can compromise the door and make it easier to break in, so here’s my guide to measuring euro-cylinder locks to ensure you get the right fit:
Remove the lock from the door, and make a note of the inside face and the exterior face, then, using a tape or ruler, measure the overall length across the faces, then measure from the inside face to the center of the cam, called dimension ‘A’, then do the same for the exterior face called Dimension ‘B’.
These 3 dimensions will give you the information you need to buy a new lock that will fit your door. but as in most things, there are several variations which I go through in the guide below:
How to measure a Euro-cylinder lock
You can measure the size lock you need in two ways, firstly with the lock fitted to the door, and the second option requires the lock to be removed, this is my preferred method as it is often easier to measure, and you will get better and more accurate dimensions.
Read our easy-to-follow guide on how to remove a euro-cylinder lock for more details on this step.
To replace your lock or upgrade your door locks, you will need to know the length and the split, this refers to the location of the cam within the lock,
A 50/50 split means the cam is in the center of the lock, at the same distance for the exterior face as the interior face, and probably the most common type of Euro-cylinder lock.
Take a look at our lock size chart below for the most common euro-cylinder lock sizes.
Using a tape or ruler, measure from the inside face to the center of the cam (dimension ‘A”) then do the same for the outer face (dimension ‘B’).
Always check the thickness of the door as well and ensure you round up the lock size, for example, if your door is 88mm wide, fit a 90mm lock, and try to keep the length as close to the door width as you can but don’t go any shorter as this means the lock won’t fit properly and can let bad weather and water into the door mechanism.
As I said before, you can also work out the length of the lock you need by measuring the thickness of the door itself, this means you don’t need to take the lock out of the door first, however, this is more fiddly than it’s worth and not as accurate, so I recommend using option 2 and removing the lock first.
What size are Euro-cylinder locks?
Euro-cylinder locks are all the same size profile so they have a universal fit, however, they can vary in length, and they range from 60mm long up to 105mm.
The location of the cam can vary too, which means they can be used in lots of different door and window mechanisms here is a list of the most common sizes and combinations, the split denotes how far the cam is positioned along the length of the lock body:
| Split | Length | Split | Length |
| 30/30 | (60mm) | 0:10:30 | (70mm) |
| 30/40 | (70mm) | 30:10:35 | (75mm) |
| 35/35 | (70mm) | 30:10:40 | (80mm) |
| 40/40 | (80mm) | 35:10:35 | (80mm) |
| 35/45 | (80mm) | 30:10:45 | (85mm) |
| 45/35 | (80mm) | 35:10:40 | (85mm) |
| 30/50 | (80mm) | 30:10:50 | (90mm) |
| 45/40 | (85mm) | 35:10:45 | (90mm) |
| 40/45 | (85mm) | 40:10:40 | (90mm) |
| 35/50 | (85mm) | 45:10:35 | (90mm) |
| 50/40 | (90mm) | 35:10:50 | (95mm) |
| 35/55 | (90mm) | 40:10:45 | (95mm) |
| 40/50 | (90mm) | 35:10:55 | (100mm) |
| 45/45 | (90mm) | 40:10:50 | (100mm) |
| 55/40 | (95mm) | 45:10:45 | (100mm) |
| 40/55 | (95mm) | 55:10:35 | (100mm) |
| 50/45 | (95mm) | 40:10:55 | (105mm) |
| 45/50 | (95mm) | 45:10:50 | (105mm) |
| 50/50 | (100mm) | ||
| 55/45 | (100mm) | ||
| 45/55 | (100mm) | ||
| 60/40 | (100mm) | ||
| 40/60 | (100mm) | ||
| 45/60 | (105mm) |
The range of euro-cylinder locks is huge with the option to have keys on both sides or a key on the outside and a thumb knob on the inside in every different size and style.
With a wide range of different materials and finishes from polished nickel plated to gold and brushed stainless steel, you will find a style that will suit your taste and match your existing door furniture.
Other advice
I hope that the information above helps you to protect your home and belongings. Please bear in mind that even the most well-defended home may not stop a really determined criminal, but improving your security and upgrading your locks should help to slow them down, giving you a much better chance of calling the police.
Stay safe and for more great information on how to improve your security and protect your home read our post on more ways to improve home security.
This article was written by: Richard Quinton – The DIY Help Desk Owner, Engineer & technical specialist.
Richard is one of the key partners in The DIY Help Desk team. He is a qualified Engineer, writer, and publisher, educated to Master’s level. He is a keen advocate of DIY and home improvements.
Richard enjoys helping others to learn new skills and reach their goals and believes that passing his knowledge and experience on through his writing is an effective way to positively impact the lifestyles and well-being of others on a larger scale.
