We almost always buy watches online and sometimes upon receiving the watch you realize it is too big for your wrist or too small. Knowing the diameter works well enough, but we all have different wrists of different shapes, so I've been thinking of a more (pseudo) scientific way to tell if the watch you are buying will fit your wrist.
This is what I've been thinking about:
j=a/b
a = your wrist perimeter
b = your wrist width
j = your wrist constant
k=(x+((y-x)/2))/2
x = watch diameter
y = watch width including the lugs
k = your watch constant
Q=j/k
0.12<Q<0.15 - the watch is right for you
Q<0.12 - the watch is too large for your wrist
Q>0.15 - the watch is too small for your wrist
I've tried this formula with a few watches I have and it seems to work. Can you please help me verify this (if you are interested of course).
Man... I have too much free time on my hands