[kbenson]

Fractions are mathematical modifiers that can applied to any quantifiable measurement. That said, I imagine they aren't generally used in professional context in metric, because they generally aren't in imperial either. You don't see architectural plans that say 1-1/2 feet, they say 1'-6". Is it common to see fractional amounts in metric when used in a professional context?

[Moru]

Usually we write everything in mm for professional context.

[kbenson]

Thanks, that's what I assumed (because it makes sense). For metric you often go two orders of magnitude smaller, but I'm thinking a good amount of the reason to usually go straight to millimeters instead of also using decimeters is that decimeters just can't easily represent many common fractions of a meter (1/4, 3/4, 1/3, 2/3), and a base 10 system can never represent some of those perfectly without resorting to a mixed format.