Are Door Knobs All The Same Size

Are Door Knobs All The Same Size? Door Knob Size Guide

When shopping for a new door knob, one of the questions people keep asking is whether the door knobs come in different sizes or they’re universal.

Door knobs are NOT the same size. They come in either 3/8 inches or 2 3/4 inches and will fit doors from 1 3/8 inches to 1 3/4 inches thick. You need to make sure that you get the correct size of door knob for your door to ensure it functions properly.

We have researched more about doorknob sizes and found some helpful info that we have shared with you below to help you pick the right size of knob for your door.

How to get the right doorknob for your door?

For you to get the perfect size of door knob, you’ll need to take a series of measurements on your door. These will go a long way in guiding you on the right door size to buy so that it will perfectly fit the door when you finally install it. Getting the perfect size also reduces hustle if you have to remove the door knob for some reason. It is also important when you are purchasing things like the best door knob covers for safety.

How to get the right doorknob for your door

1. Measure the diameter of the circular hole

One of the measurements you need to take to help you decide the right size of doorknob to get is the diameter of the borehole on your door.

You can do this by measuring across the circular hole. For more accurate results, be sure to measure across its widest point (that is, put a tape measure at the bottom of the hole and pull it all the way up to the top of the hole).

Measure the diameter of the circular hole

Once you have obtained the diameter, note it down on a piece of paper or in your notepad for reference.

2. Measure the distance from the hole to the door edge

Next, you’ll need to measure the distance running from the circular hole all the way to the door edge (also known as the backset).

This distance is usually 2 3/8 or 2 ¾ inches, so you should obtain these exact measurements. A slight deviation is allowed, though.

Measure the distance from the hole to the door edge

To get this backset distance, place the tape measure on the center of your door hole and pull it all the way to the edge of your door.

Read the measurement and note it on your notepad as well.

3. Measure the door thickness

The last measurement you need to take is how thick your door is.

This is as simple as placing your tape measure on the left edge of the door and pulling it all the way up to the right edge of the door.

If you’re measuring an interior door, you should get a measurement of around 1 3/8 inches thick. And if you’re measuring an exterior door, it should measure 1 3/4 inches thick.

You need to make sure you’re dealing with a door of an average thickness (in accordance with these measurements). You can also try to match your knobs with hinges at this point.

Measure the door thickness

Otherwise, you might need to invest in special hardware to facilitate correct door knob installation.

Remember to note the measurement on your notepad.

Choosing the right size of door knob

Having obtained the above measurements, now it’s time to choose a knob that corresponds to them. How exactly do you do it?

Choosing the right size of door knob

This is what we’re going to teach you in this part.

Borehole diameter

Firstly, you should look at the diameter of your new knob. it should match the diameter of the circular hole on your door for the perfect fit and proper installation.

Borehole diameter


As for the backset, some door knobs come with an adjustable backset to let you fine-tune them according to the specific size of your door backset.

If your new hardware comes with this feature, then you won’t have to worry much about the sizing.

But if it doesn’t, you have to stay specific to the size of the backset measurement you obtained above.



You don’t want to get a doorknob that’s thicker than your door. If you do, the hardware will look out of place.

Luckily, most manufacturers produce their door knobs with interior and exterior door thicknesses in mind. this way, it becomes easier for you to the right size of the knob.


If you find out that your door is much thicker than the average values provided above, you might consider contacting a door hardware manufacturer to see if they can come up with something specially tailored to work for you.

Final verdict

Door knobs don’t come in a standard size. They have varying sizes which means you need to ensure you get the right size that perfectly fits your door. Your door borehole, backset, and thickness are the key measurements you need to take before you start selecting door hardware to guide you into making the right choice.

Some door knobs also come with adjustable sizes which means you can easily adjust them to fit your specific door size. Just make sure you take these measurements with you to the store and you’ll get the right knob for you.

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