WatchDetails and Components. 1. Watch case diameter as the most obvious parameter of size usually ranges from 33 – 45 mm. If we break it down to stereotypical categories, then anything under 37 mm diameter would be put into boxes such as “jewelry/elegant category” and “women’s size watch”. Meanwhile, the rest are “men’s size Selectingthe right watch involves more than just aesthetics; it's a matter of finding the perfect fit for your wrist. Here's the quick guide on how to choose the right watch size to ensure both style and comfort. 1. Case Diameter: Begin by considering the case diameter. Watches come in various sizes, and choosing the right diameter is crucial. .