How to measure for a new doorset

If you want to change an entire door unit you'll probably want to buy a doorset or door assembly, so that both frame and door leaf will be replaced. Doorsets are typically sold as French door sets , for more than one door leaf, or as door set frames , ready assembled single doorsets. If this is the case you shouldn't take the measurements from the old door or frame, you'll need to measure the rough opening in the walls. The doorway without any frame is usually called a rough opening or a structural opening.  

These measurements will be for the external dimensions of the door frame, which is how door set size's are usually given. The size of the door leaf will be dictated by the size and type of frame. Some frames are thicker than others, but the door leaf will fit the specific frame. 

Before you begin

You'll need to remove the old door, frame, and architrave for the most accurate measurements. If you can't do this you will still need to remove the architrave so you can see where the frame meets the wall. You should use a tape measure used for construction or carpentry, that can remain stiff when extended, rather than a flexible measuring tape. Take the measurements in millimetres as this will be more accurate.

For more information see: How to remove an old door and How to remove an old door frame and architrave 

Step 1 - Measure height

Measure the height of the opening from the head of the doorway to the floor or sill. Make sure you take into account the type of flooring you have, especially if it has not been installed yet. Take measurements from three different places for each dimension and use the smallest. Take away 10mm from the final measurement.

Step 2 - Measure width

Measure the width from wall to wall. Take three measurements across the top, middle and bottom of the walls, use the smallest measurement and take away 10mm.   

Step 3 - Measure thickness

Measure the thickness of the rough opening. It's best to take two or three measurements for this also. Find the thickness which is the closest match for the door set you want. If there is any architrave or trim around the rough opening make sure you don't include this in your measurement. Remember, exterior walls are usually much thicker than interior walls.