How to measure a door frame correctly

Internal UK doors are generally made in several standard sizes to meet most domestic needs. However, not everyone is lucky enough to have a frame to fit a standard sized door.

Internal doors in the UK are generally made in several standard sizes to meet most domestic needs. However, not everyone is lucky enough to have a frame to fit a standard sized door.

In these instances, you will have to go to a little more effort in order to determine your sizing and select a door that fits into the opening where the door should be. But don’t worry, it’s not too difficult as you’ll soon see below.

XL Joinery doors can be ordered in many different sizes including both standard imperial and metric sizes, and can also be shaved to fit your frame. By following these steps, you will be able to accurately measure your door. Don’t worry if you find that your door seems to be an odd size, as you can check out our made to measure service.

How do you measure internal doors?

If you only have a frame without the door, you will have to take the measurements from the frame itself, which can be a little bit more time consuming than measuring the door.

To get started, you will need a tape measure, a pen and some paper.

Start by laying a large protective sheet or covering on the floor. Carefully unscrew the hinges from the frame and lay the door flat on the sheet. Take out your measuring tape and simply measure and mark down the doors.

How do I measure door height?

Measure both the left and right side of the frame from top to bottom to determine the height of the door required. It is essential to measure both sides as the frame may not be completely level, therefore the door may have to be taller on one side than the other to ensure a proper fit with no gaps.  Always go with the larger measurement. Remember to add approximately 3mm of clearance.

How do I measure door width?

To measure the width, you need to measure the top of the FRAME from left to right, as well as the bottom of the FRAME from left to right.  This is for the same principle as measuring two points for the height, as it allows for an accurate reading in order to ensure a proper fit. Again, always go with the larger measurement. The clearance between the bottom edge of the door and the floor will depend on the floor covering and any threshold strips that may be fitted.

Measuring the door thickness

There are only three standard sizes of thicknesses for doors (35mm, 40mm, and a 44mm fire door). The thickness is relatively straightforward to work out; just measure the thickness of the frame from inside to out. Picturing where you would like the door to sit and you’ll be able to see exactly where you need to measure.

To learn more about installing and trimming a door please view our instructional videos here.

XL Joinery offer a comprehensive range of oak doors, including grey and black doors. For more information about our collection please download our catalogue or visit our website

It is important to measure in a number of places to gives you an accurate depiction of the door as the frame and door could have warped since it was first put up and many people who haven’t measured a door themselves forget this part.


Our website uses cookies to enable the quote basket to function, but these contain no personally identifiable information. The site also collects anonymous usage data via Google Analytics to allow us to examine the effectiveness of our website.

Privacy Policy Accept Cookies