We start from your height and map it to a typical stack/reach band used by modern frame charts — a mid-170 cm rider lands near M / 54. Inseam, torso, and arm proportions nudge that target, and we soft-check traditional seat-tube size with the Guimard rule (inseam × 0.67).

Each catalog size is scored by how far its published stack and reach sit from that target — too big is penalized harder than slightly small — and we keep the best size per bike. A published rider-height chart (e.g. 172–178 cm) adds a soft penalty outside its band, never a hard reject. Published standover does hard-reject sizes where clearance (inseam − standover) is too tight for the bike type, and seat-tube angle is flagged when it may fight longer-femur proportions.

This is a list of likely sizes worked out from the published numbers, not a full bike fit — open one on the fit page to try the saddle and bars before you buy.