How to measure Lego part's dimensions for a Fan-designs?


I didn’t know where I’d have asked my questions regarding this subject, so I made this topic.
(To the Mods: Feel free to delete or move the topic if it’s in the wrong category!)

I really need your help regarding this issue I have lately:
I’ve been working on a G3 fan project, which I plan to develop further to turn it into an actual pitch.
However, I’ve run into some problems I can’t figure out.

My question is: What is the best way or method to accurately measure the dimensions & proportions of official Lego element’s parts?

I am primarily interested in the more unique and special parts’ physical attributes, such as the radius of the Mixel/tow ball joint or the overall dimensions of the Mixel socket joint.

If you can recommend info sources or tools I could use to calculate the rates of these parts’ please send me a few suggestions in the replies!

Thanks! :v:


I admit I haven’t a lot of experience in this area but if you have a decently precise caliper you should be able to get some fairly accurate measurements. If you measure the diameter of the tow ball as well, you should theoretically be able to mathematically deduce what the size of the socket is. There may also be official dimensions somewhere on the internet.

Hope this helped at least a little, and good luck with your project!


I’ll say that if you’re pitching, unless you’re going for a fully functional working prototype, the focus should be on developing the concept.

You can worry about perfecting the compatibility if Lego ever accepts their pitch, which if they did, they’ll spend time fine tuning it, incl. compatibility.

Also, if you’re doing digitally, you can always export files.

TL;DR your proof-of-concept doesn’t need to be precise, it just needs to be a prototype proving your concept.


Are you looking for the nominal dimensions or the physical dimensions?

Unless you plan to injection-mold your own custom parts, the nominal dimensions should be fine, and the basic nominal dimensions of Lego parts are well-documented online.

The towballs and their sockets have a nominal diameter of 5.9 mm.


Bricklink has information on the dimensions of most pieces


That’s the package dimensions. It’s useful for determining if the piece fits in a box/bag for delivery, but it’s not really useful for modelling.


Ah, didn’t realize that, thanks for pointing it out