I have the Castelli 'Inferno' bib shorts, and, like other brands, Medium fit fine.
However, I just got their Volata jersey. Normally I am a medium in cycling jerseys but the fine reviewers on Amazon said order a size up so I did and went large. Glad I did too.

I'm just a tad under 5-8 and weigh about 157. Inseam about 31-ish.

Hope that helps.

BTW I'm very happy with Castelli stuff so far (it is pricy though).