Choosing Your Case Size: 40mm vs 45mm

The single question we receive most often from first-time buyers has nothing to do with movements or complications. It is almost always this: what size watch should I buy? It seems simple. It is not.

Case diameter is a measurement of the dial's circular face, taken at three o'clock and nine o'clock. What it does not measure is lug-to-lug distance — the span between the two sets of lugs that defines how far the watch extends up and down your wrist. A 42mm watch with long lugs can wear larger than a 45mm with short ones. The number on the spec sheet is a starting point, not an answer.

A useful rule of thumb: for a wrist between 16cm and 18cm in circumference, a case between 38mm and 42mm will generally proportion well. For wrists above 18cm, 42mm to 44mm sits naturally. Beyond 44mm, you are in territory that is genuinely bold — it will read, and it is meant to. If your wrist sits closer to 15cm or below, 36mm to 38mm is historically the territory that fits without overhang.

The most reliable method remains the same one watch dealers have used for decades: try the watch on. Ask for a loaner strap if the bracelet does not match your size, and note how the lugs sit relative to your wrist edge. A watch that extends past the wrist bone will never feel quite right, regardless of how good it looks on a display stand. Wear it, move your wrist, pull back a cuff, and then decide.