I am trying to build my own furniture using MDF(medium density fiberboard)boards. I want to open my box pulling up the door(see below), but the door flap is too tight. Since the door jams, I have to trim it a little bit. But how much?

Thanks for your help.enter image description here

  • 1
    One of the traditional ways this was done was not to increase the whole gap but instead leave it tight at the front for a good appearance, but to make the door easy to open you 'relieve' or back-cut the edge of the door opposite the hinge. This edge can end up a flat angle or a smooth curve, it doesn't matter, use whichever is easiest to do or you like the look of most. P.S. It's MDF in English also.
    – Graphus
    Commented Aug 29, 2019 at 13:36

1 Answer 1


The exact amount you need can be calculated using the pythagorean theorem. See the modified diagram below, with a triangle overlayed on it:

enter image description here

You already labeled the 16mm dimension. You then need to measure X (the distance of the opening). From there you can use a^2 + b^2 = c^2 (or to plug in the values on the diagram, 16^2 + X^2 = Y^2; to change it around we get: Y = SQRT(X^2 + 256).

That will give you the length of the dimension Y. You can then subtract X from that number to get the amount that needs to be cut.

For instance, assume the door size is 600mm. You can plug that in for X, and will get:

Y = SQRT(600^2 + 256)
Y = SQRT(360256)
Y = 600.21

So, you would only need to trim 0.21mm off in this case.

If the door was smaller, this value would be larger; for instance a 200mm door would result in a 0.64mm difference.

As @Graphus indicated in their comment, you can also cut this at an angle, so that the front of the door is flush and the back of the door is shorter. This calculation will still apply to determine how much you need to cut.

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