If you were to picture your idea body proportions and shape you've probably got an image of wide shoulders and a narrow waist (or at least you SHOULD have this image in your head). But what you might not be focusing in on is the exact size of your shoulder compared to your waist.
In order to calculate your ideal shoulder size you first have to know your ideal waist size. BUT in order to know your ideal waist size you have to start with your height. The calculation goes from your height to your waist to your shoulders.
Your ideal waist size is going to be between 45%-47% of your height. In other words, if you're 70 inches tall you're ideal waist is between 31.5 - 33 inches.
This calculation is based on bone structure and a low level of fat mass. Once you have determined your ideal waist the next calculation is your shoulders.
Based on all of the proportion and physical attraction research we know that the ideal ratio of waist to shoulders is a ratio of 1:1.618. Going back to our example of 70 inches height and a 31.5 - 33 inch waist your idea shoulder circumference would be 1.618 times larger than your idea waist or 51 - 53 inches.
The ideal shoulder to waist ratio only holds when you're waist is in its ideal range. In other words, having a waist that is 50% of your height and shoulder that are 1.618 times larger than this is not going to produce the proportions you are looking for. And in fact you will find it very hard to build your shoulders to this degree to offset the bulk of your waist. This will also produce a shorter stalky look that is not ideal. Your best proportioned body shape must start by accounting for your height, otherwise there is no way of determining what waist size and shoulder size is too think and too thin.
Follow this measurement pattern starting with your height --> ideal waist --> ideal shoulders and you are on your way to building your best proportioned body.