How to Trim a Door to Size

Internal doors are made in several standardised sizes. Most modern doors are 1981mm x 762mm, but there are bigger and smaller doors on the market too. If you live in a property that has unusually sized door openings, you may find it difficult to find the door you want in a size that matches the opening. The best solution is to buy a door that is slightly too large and trim it down to fit.

Tools Needed:

  • Screwdriver
  • Saw
  • Screws
  • Tape Measure
  • Smoothing Plane or sandpaper
  • Pencil
  • Marking guage or Stanley knife
  • Straight piece of wood (or similar - for marking where you want to trim)

Step By Step Instructions

1. The first thing that you should do is measure the door opening. In most cases, the door will be the right height, but too wide. Take three measurements for the width of the door - one at the top, one at the middle and one at the bottom. The narrowest measurement is the one that you want to work with.

2. If the door has any fittings (such as a hinges) attached to it, remove those.

3. Lay the door on its side with the hinge mortise up. If you have an old door that fit the door opening perfectly, you can use that to help you mark out the new door's measurements. If not, you will need to measure the door and place pencil marks where the cuts should go.

4. Set the marking gauge to your pencil marks and run along door to be cut, this will create a cut line that will guide your saw. Alternatively, place a straight piece of wood (or similar) along your pencil marks, andyou can use a stanley knife to create a cut line.

5. Slowly and carefully start sawing the door down to size. It is vital that you work carefully here, and err on the side of not removing enough wood from the door. It is better to have to repeat the cutting process a few times than to take away too much wood and end up with a door that is to small.

6. Once the door is an almost perfect fit, you can finish the job by using a smoothing plane or some sandpaper to smooth out the area that has been cut. If you have removed a lot of wood from the door then you will need to make new slots for the hinges. When fitting the hinges, make sure that the chisel cuts only across the grain of the door - cutting along the grain could cause the wood to split.

Tips and Tricks

  • Remove only as much wood as is absolutely necessary to get the door to fit. If you remove too much, then you will end up with a door that lets draughts into your home.  When re-fitting hinges and other fittings, work with the grain, and be sure to drill a pilot hole for any screws that need inserting. If you try to cut corners you run the risk of splitting the wood.
  • If your door has three hinges, fit the top and bottom ones first and leave the middle hinge until the door is in place.



  • Information is accurate at time of publishing, however, may be subject to change.
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