Watch Size Calculator
Case diameter and lug-to-lug for your wrist.
Find the watch case size that suits your wrist, with the lug-to-lug limit that actually decides whether a watch fits.
Case diameter
42 mm
40–44 mm suits this wrist
Lug-to-lug decides whether a watch fits, not diameter. A 40 mm case with long lugs can overhang a wrist that a 44 mm case with short ones sits comfortably on, because what matters is the span across the flat of the wrist.
How the Watch Size Calculator works
Case diameter is the number watches are sold on and lug-to-lug is the number that decides whether one fits. A 40 mm case with long lugs can overhang a wrist that a 44 mm case with short ones sits comfortably on, because what matters is the distance across the flat of the wrist, not the diameter of the dial.
Also known as: watch case size calculator · wrist to watch size
Lug-to-lug, not diameter
Case diameter is how watches are marketed and lug-to-lug is what determines whether one fits. The lugs are the horns the strap attaches to, and the distance from tip to tip is what spans the flat of the wrist.
A 40 mm case with long lugs can measure 50 mm lug-to-lug and overhang a wrist that a 44 mm case with short, curved lugs sits comfortably on. Diameter alone tells you very little.
The usable flat of a wrist is roughly 85% of its circumference divided by pi. Anything with a lug-to-lug beyond that will overhang, however good the diameter sounds.
A worked example
A 7 inch wrist is 178 mm around, giving a usable flat of roughly 48 mm. A case in the 40 to 44 mm range suits it, but a 40 mm diver with 50 mm lug-to-lug will still overhang, while a 44 mm dress watch with 46 mm lug-to-lug will not.
This is why trying a watch on beats every chart, and why published case diameters mislead so consistently in online buying.
Where the answer misleads
Thickness matters for comfort and for cuffs, and no diameter figure captures it. Under about 12 mm sits under a shirt cuff comfortably; above 14 mm generally does not, and a thick case on a small wrist looks top-heavy regardless of diameter.
Fashion moves the convention substantially. Cases fashionable at 34 mm in the 1960s and 46 mm in the 2010s both fitted the same wrists; what is 'correct' is largely what people are used to seeing. The ranges here are conventions, not rules.
Finally, strap and bracelet design changes how a watch wears. A bracelet that hugs the wrist makes a large case sit more securely than a stiff strap does, which is why the same head feels different on different bands.
Frequently asked questions
What size watch should I wear?
As a starting point, a 6 inch wrist suits about 36 to 40 mm, a 7 inch wrist 40 to 44, and an 8 inch wrist 44 to 48. Those are conventions rather than rules, and personal preference moves them by several millimetres in either direction.
What is lug-to-lug and why does it matter more?
The distance from the tip of one lug to the other, which is what actually spans the wrist. If it exceeds the flat width of your wrist the lugs overhang and the watch sits badly however good the diameter looks on paper.
How do I measure my wrist?
Wrap a tape round the wrist bone where the watch sits. For lug-to-lug, the usable flat width is roughly 85% of that circumference divided by pi — but eyeballing whether the lugs reach the edge of the flat is just as reliable.
Does case thickness matter?
For comfort and cuffs, yes. A thick case on a small wrist looks top-heavy and catches on sleeves. Under about 12 mm sits under a shirt cuff comfortably; above 14 mm generally does not.