I checked the few group pics where they stand almost standing straight, and almost at the same scale, to see how the size comparison match up :

according to the Wiki, 2D is 1m88, noodle is 1m57 (idk if its when she’s adult or not tho, i couldn’t find infos abt that???) and Russel is 1m75.

^^^ on this they aren’t on the same line so i don’t know how much i can do an estimation

now, it is very inconsistent in the canon because Murdoc seem to get randomly shorter and taller depending on the drawings

like on this illustration for their collab with a brand of shoes :

it look like they inverted their sizes, and murd seem edited too big, he feels out of place. (or maybe its just me???)

on this more recent pic he has pretty much the same height as on the first pic,  wich is his head ariving around 2D’s eyebrows height

so their size difference is really not THAT extreme

BUT now if we look at the song machine MVs,

(screenshot from @plratejet)

He seem to be even shorter than noodle,(but again i’m not sure about her size so-) - and 2D could easily put his chin on the top of Murdoc’s head.

so he aither get shorter with time because he’s old, or the artists dont have a proper reference sheet but maybe it’s on purpose, what do i know-

i made the band in DesignDoll, (respectevly, Phase 3 noodle, 2D, Murdoc, Russel and phase 5/6 Noodle),  i mostly used phase 1 to 3 artworks as reference for them, but as shown in the Song machine pic, their size stayed pretty much the same (except noodle, ofc)

SO,

IN CONCLUSION,

to me, MURDOC IS 1m77

wich isn’t that short, but still shorter than 2D, and i think that’s important-