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How to Measure a Door Lock Cylinder

This article is a collaborative effort, crafted and edited by a team of dedicated professionals.

Contributors: Muhammad Baballe Ahmad, Mehmet Cavas, Sudhir Chitnis, and Zhen-ya Liu.

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How to Measure a Door Lock Cylinder . In order to ensure that you’re getting the right size door lock cylinder, it’s important to measure it correctly.


Measuring a door lock cylinder retaining can be an important part of ensuring the proper fit and security of a door. The measurements of the cylinder can be tricky but can be accurately determined with the right tools and steps. This guide will provide step-by-step instructions and helpful tips to properly measure a door lock cylinder retaining.

What is a door lock cylinder?

A door lock cylinder, also known as a cylinder lock, is a type of lock that uses a cylindrical key to operate. It consists of several parts, including the plug (which is the part that turns when operated by the key), pins, and springs. The plug typically has several grooves cut into it along its length – these grooves must fit accurately with the spacing of the pins in order for it to open.

The cylinder lock is often used on doors because of its convenience and ease-of-use. It can be installed quickly and easily, without requiring extensive modifications or additional materials. Additionally, they are relatively small and therefore don’t take up too much space when mounted into a door frame – this makes them particularly suited for applications where space is limited.

In order to accurately measure a door lock cylinder, you will need to measure two main components: the backset (the distance between the edge of the door frame and centre of the key hole) and the faceplate (the plate surrounding the key hole). You will also need to measure any additional screws or mounting brackets required for installation.

Why is it important to measure a door lock cylinder?

Knowing how to measure a door lock cylinder correctly is important for ensuring that you have the right replacement parts when undertaking any maintenance or repair on your lockset. The size of the lock cylinder affects both the aesthetic and practical operation of the lock. Therefore, accurately measuring your lock will help you gain access to compatible replacement parts and ensure that your security system has its maximum integrity.

For most locks, measurements will consist of two different components. Firstly, the outside dimension of the lock cylinder will generally include a length and width measurement. Secondly, some locks also require special attention to a backset distance measurement that determines how far from the edge of the door frame it sits. This measurement will influence which type of latch or deadbolt can be installed in combination with the chosen lock cylinder.

Both measurements must be considered before attempting to replace any part of a door locking system and knowing how to accurately measure a door lock cylinder is essential for satisfying practical needs as well as security requirements. Following is an outline on how these measurements may be taken so that you can find exactly what you need when performing repairs or changes to your locksets.

Tools Needed

To successfully measure a door lock cylinder, you will need a few tools. The most important tool you will need is a measuring tape, but you may also want a pair of needle-nose pliers and a marker or pen. Depending on the type of lock you have, you may also need some other specialized tools. In this section, we will discuss the tools you will need to measure a door lock cylinder.

Tape measure

A tape measure is an essential tool for measuring a door lock cylinder. This tool allows you to accurately measure the length and diameter of the cylinder, which are both important parts of identifying the right part for your door lock. To use a tape measure, simply stretch the measuring tape out along the length of the lock cylinder and read off the measurements, noting down in inches or centimeters as appropriate according to your desired unit of measurement. You should also use a tape measure to check whether or not any components protrude from either end of the lock cylinder, such as screws or other accessories that can affect how it fits into place. It’s important to be precise with these measurements so you get an exact fit when purchasing a replacement part.

Pen and paper

Before beginning this project, it is important to gather the right tools. The most commonly used tool for measuring a door lock cylinder is a measuring tape, but it is also possible to measure the cylinder with nothing more than a pen and paper.

To begin, place the paper (or cardboard) against the back of the cylinder with one line drawn along its top edge and one along its bottom. Using your pen or pencil, draw dots at each end of the cylinder’s body very lightly onto the paper. Make sure you press gently so you don’t make any holes in your paper!

Now, measure from dot to dot using your ruler or other straight edge-such as a steel level or yardstick-to get an estimate of how deep the cylinder is. Mark down your measurements and then remove your paper or cardboard from inside the keyhole; you do not need it anymore.

The next step will be to measure both sides of the keyway that feeds into and out of the lock cylinder by placing either an awl, drill bit or narrow dowel into each end in order to measure its length and width precisely. Jot down those measurements as well; they will come in handy later when selecting a compatible lock cylinder for replacement purposes.

Measuring the Inside of the Door Lock Cylinder

If you want to measure a door lock cylinder, you’ll need to start by measuring the inside of the cylinder. This is important so you can make sure you get a cylinder that fits the hole in your door. You’ll need to measure the diameter and length of the cylinder in order to make sure you get the right size. This guide will walk you through the different steps of measuring the inside of a door lock cylinder.

Remove the old lock cylinder

To measure the inside of the door lock cylinder, first remove the old lock cylinder from the door. This may require a small flat-head screwdriver, a hex key or an Allen wrench. Look at both sides of the existing lockset to determine how it is held in place and if there are any associated lock and screws. Once you have identified how the cylinder is attached, loosen and remove it by unscrewing and releasing any clips or bolts. Carefully slide the cylinder out and be sure to keep track of any parts and pieces as you go. Make sure to safely store the lock and screws until you’re ready to install your new lockset.

Measure the length of the cylinder

The length of the door lock cylinder is one of the most important elements to consider when selecting a new lock for your house. Measuring it correctly is essential for a proper installation, so it’s important to have the correct tools and know-how before attempting this task.

In order to measure the cylinder part of your doorlock, you will need a ruler and either calipers or thin paper strips cut into multiples of 1/16th inch thicknesses. If you are using calipers, take note of any make markings or names located on the cylinder itself in case you need additional information when purchasing replacement parts, such as cylinder retaining screws.

To measure the length, simply position your measuring tool inside both ends of the cylinder while running it along its full circumference until you can assess both ends completely. Write down this measurement and also note how often cylinders repeat in terms of placement around the entire circumference; for example, if there are five pins running on opposite sides, then your cylinder will likely have five associated measurements as well. As long as these numbers match those found on compatible locks during your search process, including any necessary cylinder retaining screws, you should be good to go with a perfect fit!

Measure the diameter of the cylinder

The first step to measuring the inside of a door lock cylinder is to find its diameter. To do this, use a caliper or tape measure to measure the outer diameter of the cylinder. This can usually be done on any type of door lock, whether it is knob-style or lever-style. When using a caliper, make sure that the jaws are securely positioned around the circumference of the cylinder before taking the measurement. Make sure that the measurement reads in metric because most locks have measurements that are given in millimeters.

Once you have measured out and noted down the diameter, you need to measure out and note down its depth as well. This step involves inserting one end of a ruler into each end of a cylinder and then measuring from one end to another with a tape measure or ruler. This will help you determine how much wall material there is between each side of the lock and thus accurately determine what length latch will fit inside it. Once these measurements have been taken, you can figure out which type of latch would fit in your specific door lock based on its size parameters.

Measuring the Outside of the Door Lock Cylinder

Measuring the outside of your door lock cylinder is the first step in ensuring that you get the right replacement lock for your door. The outside of the cylinder needs to be measured carefully in order to determine the size and shape for the replacement lock. This guide will go over the steps to accurately measure the outside of a door lock cylinder.

Measure the length of the cylinder

When measuring a door lock cylinder, it’s best to start by measuring the length of the cylinder. To do this, measure from the top of the cylinder to just past the edge of the mounting plate at the bottom. This measurement should be precise and include any grooves or burrs that protrude from the tip. Knowing this length is necessary since it will determine which screws will be required for installation. It is helpful to have someone else hold a ruler or measuring tape against the outside of the cylinder while you take your measurements. Once you have determined the length, record it and move on to measuring other aspects of your door lock cylinder.

Measure the width of the cylinder

Before you purchase a new door lock cylinder, it’s important to measure the outside of the cylinder and make sure you are selecting the correct size. Measure from edge to edge across the widest part of the cylinder to determine the width. The measurement should be taken while the door is closed and latched; this will ensure that you have an accurate measurement of your lock components.

The width measurements most commonly used are 2- inches, 2- inches, and 3- inches. Once you have a general idea of what size your door needs, use a tape measure or ruler to more accurately ascertain your specific size by measuring across from edge to edge at the widest point. For example, if your measurements fall between 2-3/8″ and 2-3/4″ then it would be considered a 2-3/4″ wide lock component.

When purchasing any type of hardware product, including a door lock cylinder, always use careful measurements and take the time to double check sizes before making any decisions — avoid costly mistakes by taking an extra few minutes to measure your lock components properly!

Measure the depth of the cylinder

Door lock cylinder measurements begin with the depth of the cylinder, also known as the backset. Make sure to measure this carefully as it will determine compatibility with any existing door hardware and what type of new hardware you will need.

To measure the backset, use a ruler or measuring tape to measure from the edge of the door to the center of the hole where your existing deadbolt is or would be inserted. Commonly found depths are 1 3/8 inches (35 mm.) and 2 3/8 inches (60 mm.), also referred to as “standard size” and “long size” respectfully.

Next, you will need to measure the radius of your cylinder. With a ruler or measuring tape, measure from one side of he cylinder hole (face plate) to its perpendicular opposite end across its circumference. To ensure accuracy, place your ruler inside of the hole and fill in any extra space with a spacer such as folded paper so that there is no play between material and ruler when making your measurements. Commonly found sizes are 5-pin traditional style locks that are 1in(25mm), 2in(50mm) or 3in(75mm). Modern electronic door locks usually come in 2 inch (57 mm.) radius sizes.


With this guide, you should now have all the information you need to find and measure the correct door lock cylinder. It’s important to ensure you have the correct measurements before ordering a new lock because if the measurements are wrong, you may find yourself with an unusable door lock. Additionally, the measurements you take may vary depending on the type of door lock you have, so make sure to double-check before ordering.

Summary of steps

In summary, measuring a door lock cylinder correctly involves the following steps:

1. Measuring the backset, which is the distance between the edge of the door to the centerline of the door knob or deadbolt hole.
2. Measuring the horizontal centerline of the door knob or deadbolt hole.
3. Measuring any other relevant dimensions such as handle height or if there is any crossover to account for on combined locksets.
4. Reconfirming your measurements with manufacturer dimensions when purchasing a new lockset.

By taking detailed measurements and confirming them with manufacturer specifications a new lockset can be accurately fitted and add extra security to your property while also providing a finished look to doors inside and out.

Tips for taking accurate measurements

Taking accurate measurements of a door lock cylinder is an important step in finding the correct replacement cylinder for your door. To ensure you take the correct measurements, here are some tips to consider:

-Use metric measurements when possible. While it’s acceptable to use imperial measurements, many modern lock systems prefer metric sizes for greater accuracy.

-Take three measurements for each dimension measured and ensure that all three agree with one another. This will help to rule out any measurement error caused by an uneven lock face.

-Measure twice and cut once. It’s better to double check your numbers than end up with an ill-fitting replacement lock cylinder.

-Look at the existing components of the locking system before taking any measurements – this includes checking what type of fixing screws are being used and what type of keyway the cylinder has (if any). Measurements taken from components that aren’t compatible with your replacement Lock cylinders won’t do you any good!

-If possible, measure from an existing template or similar sample so that you get accurate dimensions every time – if this isn’t available then use a precision ruler or Vernier caliper for taking exact readings.

By following these steps, you should be able to accurately measure up a door lock cylinder and find a suitable replacement without too much hassle!

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