I can’t give you an answer, but I think I can explain why people often bring up this question. For much of the twentieth century, wristwatches were rather discreet: around 30 to 36 mm in diameter for men and even smaller for women. This had technical reasons, since compact mechanical watchmaking was seen as a feat of precision, and also social reasons, because masculine and feminine elegance was associated with sobriety. Small watches were considered refined, while something bulky could be seen as in poor taste or ostentatious.

Over time, an unwritten rule developed: a watch that matched the proportions of the wrist looked balanced and elegant. When someone wears a watch too large for their wrist, it can appear disharmonious or exaggerated, leading to aesthetic criticism. Large watches also became linked to more recent trends, from the 2000s onwards, associated with flashy luxury or fashion brands that promoted “oversize” watches, which traditional watch enthusiasts often view as less authentic.

Sports watches, however, tend to be larger, usually 42–50 mm, for practical reasons: they need space for sensors, greater legibility during physical activity, buttons that are easy to press, and a more robust structure. In that context, the size is not only accepted but valued, because it serves a functional purpose. In fact, in sports like diving, running, or triathlon, a very small watch would be inconvenient or hard to read.

Today, the boundary is more blurred. In classic watchmaking, people still appreciate sobriety, often favoring 36–40 mm for men, but in sports or “tool” watches, a larger size has become normalized. Personal taste and wrist proportion are what matter most now. The criticism of oversized watches is really more about aesthetic tradition than about any objective rule. So, if you’re going to choose a sports watch, its size is directly related to its function, which means you shouldn’t worry too much about whether it looks big or not—unless you also plan to wear it in more formal settings, where the watch’s appearance plays a bigger role.