It depends on when and what you are wearing it for:
Seiko Sumo 45mm - weekend watch
Omega Titanium Seamaster 41.5mm - weekend and sometime work
Rolex Oyster Perpetual Date - 34mm - grandfathers 1964 - work and dress
Panerai (PAM535) - 42mm - weekend watch.
Breitling Colt - 37.6mm - work watch
Here are some wrist shots that I had handy. I have a 7" wrist, approx.



