Revolar is reader-supported. When you buy through links on our site, we may earn an affiliate commission. Learn more

What is a Lock Backset? How to Measure It?

Fact checked by Teddy B.Miller

what is a lock backset

Knowing the lock backset is crucial when acquiring new locks or ordering new doors for your home to guarantee correct drilling and installation. This measurement denotes the distance between the lock and the door’s edge.

Such a measurement can be found in the installation details of all lock types. And now that you know what is a lock backset, you might want to read further to determine your backset size and its purpose.

Definition of a Lock Backset


A backset on a door is the measurement between the door lock and the edge of the door, typically in inches. The backset mean for door hardware can be used as a reference to the exact measurement of the locking device you want to install on your door.

The centerline of the hole for your locking device can be used as a reference point, as the backset is measured from this centerline to the door edge. This is due to the fact that when doors are fitted with doorknobs, a circular hole is drilled into the door, necessitating information about the backset for precise installation.

What Are the Lock Backset Sizes?

In the lock backset definition, there are two standard measurements that are typically used by the US and Canada.

These are the 2 ⅜ backset vs 2 ¾ inches backset.

The 2 ⅜ inches backset is the most common door handle backsets used. It is because they are commonly used in residential doors.

On the other hand, the 2 ¾ inches standard backset can be found in commercial doors. They are used in hotels, businesses, and entertainment spots.

What Are Lock Backsets Used for?

The lock backsets, such as the backset on a window lock, are universally used for all types and models of locking devices, including handle sets, deadbolts, mortise locks, and cylindrical locks.

However, some lock backset sizes may not be suitable to the locking device that you have if it is not in the standard size.

The measurement of deadbolt backsets and the locking device can be different as it depends on the model, the type of lock, the hardware design, and the region where you purchased the locking device.

What is the Purpose of a Lock Backset?

Door hardware backset is measured in order for homeowners or business owners to buy the correct locking device with the appropriate measurement. Door manufacturers also use the lock backset measurement to drill a hole correctly in the door with accurate measurement.

Since most locking devices can only work using one backset dimension, drilling a hole with a wrong measurement would result in either the bolt not extending enough to lock the door or extending too long for the bolt receiver.

How to Measure It?

Measuring a door knob backset would only require you to have your measuring tape. To measure your lock backset, follow these simple steps:

  • Step 1: Prepare your measuring tape. Make sure to look at inches, as lock backsets are typically in inches.
  • Step 2: Open your door. This will allow the tape measure to be easily positioned from end to end.
  • Step 3: Grab your tape measure. Put the end of the tape measure to the edge of the door, ensuring the end attaches to the edge and does not slip.
  • Step 4: Pull the tape measure across the deadbolt and on top of the doorknob. The tape measure should be flushed on the door and in a horizontally straight orientation.
  • Step 5: Read the measurement in inches. The measurement of your backset should be from the edge of the door to the center of the door knob.



How to determine the backset of your door?

If you are living in either the US or Canada, your backset will typically either be 2 ⅜ inches backset or 2 ¾ inches backset. To ensure you have the correct measurement, you can measure it with your measuring tape and follow the steps above.

If your backset is not either, you might want to call a door company and ask for a locking device that will fit your specific backset measurement.

Tips to change the backset on my entry latch

Fitting your entry latch on your door is simple, but it might get complicated if your latch does not match the measurement of your backset. To change the backset on your entry latch, you might want to follow this instruction:

  • Measure the door backset first. Take your measuring tape and measure the space between the edge of your door to the center of the door knob hole, and take note of the measurement.
  • Take your latch and observe the label on the latch. The latch will contain labels on the top of the indention, which is 2 ⅜ and 2 ¾.
  • Choose the appropriate measurement. Slide the mechanism inside the entry latch to the correct backset measurement by pushing it backward or forward.

Now, your entry latch can be installed on your door.

What is the most common backset?

The most common and the standard door backset is 2 ⅜ inches. Although, the 2 ¾ inches is also popular, especially in exterior doors.


The knowledge of being handy will save you a lot of money and time, instead of calling a handyman.

You can always revisit this article if you want a refresher on the backset meaning. To know ‘what is a lock backset?’ is important, especially when you design your own house.

5/5 - (2 votes)