I'm looking for the exact dimensions of the studless Technic beams. I found a number of answers for studded beams but there are some more aspects for the studless beams which are not covered.

I'm especially interested in these parts:

  • 1
    What level of precision do you need?
    – pcantin
    Dec 22, 2012 at 16:10

2 Answers 2


Liftarms are 1 stud wide (8 mm) and 7 mm high so they have a 7:8 aspect ratio. (width is the direction parallel to they axis of rotation of the peg holes).

As pictured in the link, the 1x9 liftarm has the hole orientated vertically. So the height is 8mm. The width is 7mm and the length is 9 x 8 mm = 72mm.

Similarly, the 5x7 open center thick has height=8mm width=5 x 8mm=40mm length = 7 x 8mm= 56mm opening width=3x8mm=24mm opening length= 5x8mm=40mm

  • That sounds reasonable. I'm just curios: Where did you find this?
    – BetaRide
    Dec 28, 2012 at 14:49
  • 2
    Sorry, should have included a reference: Chapter 1 of THE UNOFFICIAL LEGO® TECHNIC BUILDER’S GUIDE Paweł “Sariel” Kmiec This is a great technic reference and doubles as a primer on mechanical engineering. Available as a free ebook in pdf form. Dec 28, 2012 at 15:17
  • 1
    PS For fun, you can also look at CAD representations of the pieces. For example, Google Sketchup, free version. You can download technic pieces into it from the marketplace and measure in the app. Assuming you trust these to be authentic and faithful renderings. You get the same dimensions I quoted above. The stud proportions are actually quite important to keep in mind when designing models. Dec 28, 2012 at 15:23

Technic, Liftarm 5 x 7 Open Center Thick

  • Height = 7.86mm
  • Width = 39.80mm
  • Length = 55.85mm
  • Opening width = 24.08mm
  • Opening length = 40.20mm

Technic, Liftarm 1 x 9 Thick (oriented as shown on Bricklink image):

  • Height = 7.86mm
  • Width = 7.44mm
  • Length = 71.36mm

(measured with digital caliper, precision +/-0.05mm)

  • Thanks for doing the measuring! Since I don't have an approriate tool, that's already helpfull. Actually I was hoping someone does now the exact values as they are weill known (and alredas answered in this forum).
    – BetaRide
    Dec 22, 2012 at 19:19
  • Thx for the dimensions, Philo did you measure other parts?
    – Brookline
    May 15, 2013 at 9:52
  • To increase precision, you can stack multiple beams
    – bb1950328
    Mar 3, 2020 at 16:12

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