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What are the real world dimensions of bricks? (starting with 1x1 brick) Plates? Studs? Does LEGO think of this in metric or imperial units or something else?

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This image shows the dimensions in LEGO Units. 1 Lego Unit is 1.6mm (the thickness of the plastic wall). In those units the stud's diameter is 3 (= 4.8mm).

enter image description here

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    +1 for Lego Unit is 1.6mm - thats the important part, everything else is based on this.
    – oezi
    Commented Oct 28, 2011 at 6:03
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    Here I clearly see what I've found by try-and-error - to connect vertical wall of bricks with vertically oriented long brick (with rails - bricks.stackexchange.com/questions/6316/…) I had to have studs on the side of wall once in 5 bricks. 5 * height = 6 * width.
    – Alex Martian
    Commented Nov 25, 2018 at 12:15
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    How much is the gap between bricks? Does this graphic take the gaps into account?
    – posfan12
    Commented Jun 13, 2019 at 1:09
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    There has to be some play, otherwise it would be hard to wiggle the parts apart from each other.
    – posfan12
    Commented Nov 4, 2019 at 0:54
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    @pcantin - Upon further analysis I believe there is definitely a allowance for play. None of my bricks are exactly integer width and length. Unfortunately I don't have enough reputation to answer this question. I measured 24 different bricks and plates. I believe the linear dimensions for width and height are exactly 8.00 mm * number of studs - 0.2 mm. When I apply this formula across my 48 measurements (24*2) I get a standard distribution of 0.016 mm. It also explains the 5.8*31.8 mm measurement from bartneck's answer
    – Carlos N
    Commented Mar 11, 2020 at 18:53
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This image from Brickipedia should sum it up nicely:

A plate is exactly one third of a brick in height (3.2 mm as in the diagram). In other words, 3 plates stack to match the height of a brick. This is useful to know if you're short on a certain size of brick, but have enough plates of the same shape and color to cover it in height.

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While LEGO uses metric nowadays, you may be interested to know that the bricks they originally copied (and bought the patent for later on) were made in the UK and thus probably used imperial measurements (although dimensions are not specified in the original patent). You may want to search for UK patent 529580 or Kiddicraft to learn more about this. There may still be remnants of that English heritage buried deep in the LEGO legacy.

Also, when LEGO started, I'm not sure what their measurements or tolerance were at the time, but they probably weren't as strict as they are now, which may account for some oddities in the system. For example, the distance between studs has been measured as 7.986mm rather than an exact 8mm.

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    I found this synopsis goes a lot further than what was generally known after the Tyco trial. There is even a thesis written on the topic.
    – Erik Olson
    Commented Oct 28, 2011 at 8:02
  • @ErikOlson either that site is gone completely(historia.com.pt), or there's a typo(historia.com maybe). historia.com/legos/clones/texts/kiddicraft.htm doesn't exist either though. web.archive.org/web/20150908034033/https://www.historia.com.pt/… might be the archived version.
    – antony.trupe
    Commented Sep 21, 2018 at 0:19
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    I used LDraw long before I learned about TLG's official use of millimeters. At some point on my own I measured a regular baseplate as being (roughly) 10 inches wide. In LDraw one baseplate is 640 units wide. Thus originally (and I still do this today even though I know it's not correct) I visualized the LDraw system as having 64 units per inch, and a 1x1 brick being 5/16 inches wide and 3/8 inches tall (ignoring the gaps between bricks). 1/16 inches happens to be very close to 1.6mm.
    – posfan12
    Commented Jun 13, 2019 at 2:40
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The precise measurements with an easy to understand technical drawing is available here. A PDF with the all the dimension is available for download.

enter image description here

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  • Why is its size 15.8 x 31.8 and not 16 x 32?
    – Tien Do
    Commented Dec 7, 2023 at 8:51
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    There needs to be a 0.2mm gap between bricks so that they can be stacked. Yes, in a virtual/ideal world, bricks could be exactly 16 x 32, but in the physical world, there are tolerances in production and friction when put together.
    – bartneck
    Commented Dec 8, 2023 at 18:32
  • Got it after reading your blog post above, thanks for your wonderful work.
    – Tien Do
    Commented Dec 10, 2023 at 14:16
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Robert Cailliau has summarized how dimensions of LEGO bricks derive from:

  • The base measure 0.8mm (that's where the 1.6mm already mentioned derives from)
  • The play measures 0.1mm (for additional space between pieces)
  • The height of studs 1.8mm

It looks like the number as the same as given in other sources, but there is disagreement about the height of a stud. I've seen the value 1.8mm (Robert), 1.7mm (Wikipedia) and 1.6mm (answers given here). Maybe the difference is because of the "LEGO" logo on top of a stud.

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    The stud height disagreement can be easily settled by examining a 1x1 headlight brick: The face with the headlight stud is inset by the 1.6mm base unit from the theoretical no-play boundary of the brick. If the stud was 1.6mm high, we should have no problem placing another brick in front of the headlight face. Even if the stud was 1.7mm high, the 0.1mm play would still allow this feat, albeit with a very tight fit. Experience shows, howerver, that we can't fit another standard brick in front of a headlight brick, indicating that the headlight stud (which is hollow, so no logo involved here) ha
    – user5544
    Commented Mar 2, 2015 at 20:41
  • Wouldn't the interior cavity and the knob need to have a clearance tolerance? Both the cavity and knob could not be 4.8 so either the knob is smaller or the side wall thickness is thinner to make for a larger opening. If you go by the graphic on Mr. Cailliau's website the side wall is 1.2 leaving a cavity of 5.4 based on the 7.8 overall dimension (8-.2=7.8). This leaves a tolerance of of .6 which is rather large. If you were to use Mr. Cailliau's clearance of .2 between mating parts the clearance diameter would be 5.2 leaving a side wall thickness of 1.3. Alternatively we could reduce bot by .
    – user5955
    Commented Jul 5, 2015 at 15:40
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    Archive of site: web.archive.org/web/20170116173744/http://www.robertcailliau.eu/…
    – posfan12
    Commented Jun 13, 2019 at 1:07
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These photos of side-by-side 2x4 bricks may be able to explain why people disagree as to the height of a Lego stud:older brick with taller studsnewer brick with shorter studs

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  • My Legos have definitely had different height studs over the years.
    – ProphetZarquon
    Commented Mar 13, 2023 at 1:55
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Lego had the moulds changed to metric.

From brightontoymuseum.co.uk website I learned that the stud width measures 4•87 or 4•88mm, so they are bigger than the 4.8mm space they go into, giving a tight fit & expanding the brick into the 0•1mm space around it.

Reading what is illegal for Lego, says Technic studs are not as tall, so going from a headlamp brick over them is okay when not so for normal bricks, as their studs are too tall. The side walls, & so also from stud to the edge were 1•5mm, then bricks with thinner 1•2mm with ribs. As I found they fit to older bricks better than the other bricks do looks like smaller space. On 1other website they found height to be under 9•6mm after measures stack of 100.

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  • Hi Andrew! I tried to edit your post to make it better readable. Please review it and correct anything where I might have misinterpreted your intention.
    – zovits
    Commented Apr 11, 2023 at 9:58
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    Do you have references for your statements? Which museum website? What "one other" website you have in mind here? What is the source of change to metric?
    – Alex
    Commented Apr 16, 2023 at 7:42
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    Your statement about the technic bricks is incorrect or misinformed. Height of the bricks is the same, stud-height also if compared with other bricks with hollow studs (no lego logo...). The illegality issue is when connecting bricks with studs on the side (like headlight bricks) with the side holes in technic bricks. As the holes are 1/10th of a millimetre lower than the side studs...
    – Michael Verschaeve
    Commented Apr 16, 2023 at 12:05

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