Tool

Compare two case sizes

Is 42 mm much bigger than 40 mm? Enter two case diameters to see them drawn to scale, and how much wider and how much more dial each step adds.

mm
mm

Case diameter, without the crown. 20 to 60 mm.

To scale

40 mm and 42 mm cases drawn to scale
Difference
– mm
Wider by
–%
More dial area
–%

The dashed circle is the first watch, the filled one the second. Dial area grows with the square of the diameter, which is why a 2 mm step can look bigger than it sounds. Thickness, bezel width and lug-to-lug change how big a watch looks too.

How the numbers are worked out

  1. Difference = larger diameter − smaller diameter.
  2. Wider by = larger ÷ smaller − 1, as a percentage.
  3. More dial area = (larger ÷ smaller)² − 1, as a percentage, since a round case face is a circle.
  4. Percentages are rounded to one decimal place.

Common size steps

SizesWider byMore dial area
36 vs 40 mm 11.1% 23.5%
38 vs 41 mm 7.9% 16.4%
40 vs 42 mm 5% 10.3%
41 vs 44 mm 7.3% 15.2%
42 vs 46 mm 9.5% 20%

See also: wrist fit calculator · browse by case size