The numbers that matter
Diameter is the number everyone quotes and the least useful one in isolation. A 38mm case with long lugs wears larger than a 40mm case with short ones. Thickness changes the read more than diameter does. Lug-to-lug decides whether a watch fits a wrist at all.
Working through it
I drew the same case at four diameters and held the renders at arm's length. Then I did it again at a fixed diameter with four lug lengths, which was far more informative.
The relationships that mattered:
- Lug-to-lug against diameter — the single ratio that governs fit.
- Thickness against diameter — governs whether it reads as a dress watch.
- Bezel width against dial opening — governs how large the watch looks versus how large it is.
None of this is original. It is simply the point at which received wisdom stopped being received and started being understood.