This may sound like a high (elementary) school type question but, given that a standard non-terminated ethernet cable needs 8mm hole, what would 2x need to comfortably fit through given the size?
It is certainly not 16mm as this hole would be far too big for 2x cables, which I've seen in the past.

  • 2
    8mm seems much. Depends in cable size, but for an cat5e UTP 5mm is realistic. 8mm perhaps for an outdoor rated FTP cat6
    – Martin
    Oct 28, 2023 at 10:04
  • 2
    Or just drill two 8mm holes....
    – Ecnerwal
    Oct 28, 2023 at 13:43
  • 1
    Is this an interior or exterior wall? If it's interior, a bit of extra room doesn't matter, plus you want extra room to be able to pull the cable through without damaging the housing. If it's exterior, you do need to be concerned with weather sealing it afterwards, but you still need some extra room to pull the cable without damage. You're not going to get a weather tight seal by making the hole the exact size of the cable...
    – FreeMan
    Oct 28, 2023 at 13:57
  • 1
    2x holes might actually end up neater, depending on the material. Oct 28, 2023 at 14:56
  • 1
    drill a hole in a piece of wood and test ... punching a hole in a piece of cardboard would also work
    – jsotola
    Oct 28, 2023 at 18:24

1 Answer 1


Cables are a bit squishy, so two things matter:

  • Area
  • Diameter

The area of a 8mm (diameter) hole is 4mm2 * pi = 50mm2.

To have 100mm2 we need an 11.2mm hole. This is may not be big enough, as the cables are not very squishy, but I would guess it's in the ballpark. I would probably try with a 12mm drill and see if both cables would fit that. Drilling to bigger diameter tends to be easier than un-drilling.

  • I might experiment with this in a piece of wood or something, since it may be annoying to drill holes in masonry to ever-slightly-larger sizes. Oct 28, 2023 at 14:20

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