Watch Sizing

Watches are typically measured in millimeters (mm), which might not be familiar to those of us without a lot of metric system experience. Any given watch typically has three measurements: case diameter, case thickness and band width.
Ex, At Amazon.com, you'll find these measurements listed in the Product Specifications section of each product detail page. For a comparison, a United States quarter measures 24.26mm in diameter (0.96 inches), comparable to an average-sized woman's watch, such as this women's TAG Heuer watch measuring 24mm (0.94 inches).

Here are some basic guidelines for thickness:
Thin: 4mm to 6mm (0.16 to 0.24 inches)
Average: 7mm to 11mm (0.28 to 0.43 inches)
Large: 12mm to 14mm (0.47 to 0.55 inches)
Extra-Large: 15mm to 18mm (0.59 to 0.71 inches)

While you can get a sense of a watch's size from its width measurement, be aware of the dial's design. Consider two watch cases that have the same measurement. One might appear larger because its dial extends to the very edge of the case, while the other seems smaller because it has a thicker bezel that frames the dial. Ultimately, this visual measurement is rather subjective.
One measurement you won't find is the weight of a watch, but one thing to keep in mind is that adding a metal bracelet will add to the watch's heft on your wrist. If weight is a concern, consider a bracelet and case made of titanium, a metal that's far lighter than stainless steel.