Size and Fit
Measurements that decide how a watch sits on the wrist, plus endurance figures like power reserve.
- Case Diameter
- Case diameter is the width of the watch case across the dial, measured in millimeters and excluding the crown. Common sizes run roughly 36 to 42mm. It is the headline size figure quoted for a watch, but lug-to-lug length does more to decide how the watch actually fits your wrist.
- Case Thickness
- Case thickness is how tall the watch stands off your wrist, measured in millimeters. Genuinely slim watches come in around 10mm or under and slip under a cuff, while most modern divers run thick, roughly 12mm and up. Thickness shapes comfort and how a watch sits as much as diameter does.
- Lug-to-Lug
- Lug-to-lug is the vertical distance from the tip of the top lug to the tip of the bottom lug. It, not the case diameter, decides whether a watch will actually fit your wrist.
- Lug Width
- Lug width is the gap between the lugs, in millimeters, where the strap fits. It is usually an even number like 18, 20, or 22mm, and it tells you which straps will fit your watch. Knowing the right figure makes buying a replacement strap easy. It is not the same as lug-to-lug, which is the overall case length.
- Power Reserve
- Power reserve is how long a fully wound mechanical watch keeps running off the wrist. On most automatics it is around 40 hours; some models reach 70 hours and beyond.
- Wrist Size
- Wrist size is the circumference of your wrist, measured with a flexible tape at the narrowest point just behind the wrist bone, usually in millimeters. That number helps you pick a case diameter, thickness, and especially lug-to-lug span so a watch sits flat instead of overhanging.