The Brick Bakery: LEGO Dimensions.

When you are building with standard (non-Technics) LEGO, you seldom have to worry about the dimensions of the parts - you build horizontal rows of bricks with the studs pointing up and everything basically "just fits". However, with Technics parts, there is greater opportunity for placing parts so that the rows of studs run at unusual angles and the question of the exact dimensions of parts becomes important.

Here is a picture that summarises most of the dimensions with examples:

Referring to the numbers in the image:

  1. The height of 5 standard bricks equals the width of 6 studs. This is a fairly awkward number to deal with - but that's life. Each stud is 8mm wide (about 5/16ths of an inch) but that doesn't matter - LEGO enthusiasts always measure things in units of 'studs'.
  2. Thin bricks ("Plates") are one-third of the height of a standard brick. Hence there are 5 plate-thicknesses for every two studs...which explains why LEGO chose to provide 1/3rd thickness plates rather than half-thickness as you might have expected.
  3. The Geometry of gear wheels seems easy at first sight. Gear teeth are named according to the number of teeth they have - so an 8t gearwheel has 8 teeth. The number of teeth is always 8 times diameter of the gear (or 16 times its radius). Hence:
...which is fine so long as you want to mount gear wheels in a line along a beam - but if you want to mount them at right angles to the rows of studs, that 5:6 relation between the size of a stud and the height of a beam makes life very messy. Figuring out the math is tricky - but follow this link for more details.
  • ...and...
  • how the holes in a beam line up with the holes in a vertical column of bricks. Notice that spacings of 3, 5 and 7 studs are possible with varying numbers of 1/3rd thickness plates.
  • LEGO chains are designed to mesh with LEGO gears. 3 links equals 2 studs.
  • This shows the relationship between the thickness of various collars. The wide grey collar is one stud long - the narrow ones are a half stud. The usual grey gears - and some wheels are also one stud thick. The worm gears are actually a shade short of two studs. Thin beams are also a half stud wide. LEGO axles are always an exact number of studs long.
  • Angled components come at a variety of angles - the angled beams bend at 45 degrees, the steep sloped bricks have a 45 degree slope on them - but the little step at the end of the brick means that when you put them together, the total slope is a little steeper than that (because of the 5:6 brick height to stud size ratio). The gently sloping bricks are 25.7 degree slopes (14 bricks make up a full circle)...but again, the slope is a little steeper when the bricks are piled up.
    Steve Baker <>