Watch sizes that fall into the 35-40mm category are typically the most common watch size for men. Watches between 35-40mm are also considered as mid size watches. If you want something that's not too big, but not too small - a timepiece inbetween 35-40mm might be the right fit! While you're thinking about what is the right watch size for you, you'll also want to think about these other main factors. Such as the watch's case thickness and the band's width.