Actually there are "ideals" that were developed from studying classic lines and symetry from the greeks.
I believe its something like: All percentages are take from your chest measurment.
Biceps: 35%
Forearm: 30%
Neck: 35%
Calves: 35%
Waist: 65%
Quads: 55%
So if you have a 50" Chest:
Your neck, calves, biceps all need to be about 17.5" to be in proportion.