It can be quite a stressful job to source the right fire door size for your requirements, we know that shopping around for the perfect door size and style can be a nightmare and you ending up with an ill-fitting door when you come to install or have someone install for you and that’s not what you want.

Follow the guide on how to measure for a new door leaf and or frame to make sure that you don’t end up with a product that either doesn’t fit or match your expectations. 

Please note that if you are buying replacement doors, DO NOT just measure the existing door and expect the replacement to fit. You must always base your measurements on either the new or existing door frame/lining. There is an old craftsman’s expression, “measure twice, cut once”, so please bear this in mind. 

Another aspect to consider when recording door measurements, is the way the door opens (known as right- or left-hand opening). Stand in front of the door, so that it opens away from you, and take a note as to whether the hinges are on the right or left side of the door. Left side hinges mean the door is left-hand opening away, whereas right side hinges mean the door is right-hand opening away. 

Step 1: Measure the door width:

determines the width of the door. 

  1. Use a tape to measure the width, hand opening away, take three measurements top middle and bottom the measurement should be from the edge where the door closes to the opposite edge, this we call rebate to rebate measurements, record these sizes in millimetres
  2. The standard widths of UK doors are 610mm, 686mm, 762mm and 838mm in 1981mm height or 726, 826 and 926 x 2040mm height.


Step 2: Measure the door height:

  1. Now use the tape to measure the height of the door frame/lining. Run the tape from the top right-hand corner to the bottom right-hand corner, then do the same on the left-hand side. The tape should run from the rebate (edge where door closes) to the floor level.
  2. Remember to take into consideration that this could be a job where you will need to stand on suitable steps etc. to reach the top of the frame rebate. Record these sizes and take the longest measurement.
  3. The standard UK height of doors is most commonly 1981mm, and 2040mm

Measure the inside of each vertical side of the frame. The longest length determines the height required. Remember to make allowance for any floor covering. 

Step 3: Measure the door thickness:

If you are looking to purchase replacement doors and to keep the same frames, you will need to replicate the door thickness, so make sure to take this measurement also. 

  1. Use a tape to understand the thickness of the existing door. Run the tape along the edge of the door and record the measurement of the thickness
  2. Measure the rebate in the frame, this is the depth where the door sits into when closed
  3. The recording of this measurement should be a close match and fit with one of the UK standard door thicknesses: 35mm is the most common, but some doors may also be 44mm and 54mm for 60-minute fire doors.