I'm reposting this here, because the question came up again on another thread. Balance fundamentally refers to the relative lengths of the front and back of a coat, and also the left and right sides. Each should appear to be the same in relation to the other. Well, actually, there is religious dispute about front-back. Some believe that the fronts should always be a hair longer at the bottom. This, I understand, is the most traditional view, and if you polled tailors, this would win. However, some prefer the bottoms to be dead even, and I even know one or two who prefer the back to be slightly longer than the front. That is decidedly a minority view. Left and right should always be dead even at the bottom. Also, the four major components (front, back, left side, right side) should not bow out or scrunch inward or bunch up. However, "relative length" is not really the whole story. If it were, you'd think that all you have to do is make sure that each part is "long" enough, and if not, well, then, lengthen it from the bottom. Right? Alas, no. We must remember that the coat is 3-D, because the body is 3-D. Balance is also a matter of ensuring that the coat's cloth properly finds its way around the body's natural contours. "Relative length" in this sense is more properly thought of as the right amount of length -- or its absence -- in the right place. Take the case of a low shoulder. A person with a drop on one side who tries on a RTW coat will notice that the coat hangs lower on his low side. The bottoms will not be even, and the buttons and buttonholes will not line up. In the worst case, the low side actually cuts away, or swings outward, rather than hanging more or less straight. If he buttons the coat, he will see the lapel on his low side bow out above the button. What he needs, therefore, is less "length" or cloth on his low side. But not merely less length. It has to be taken out from the top of the front and back parts. Either that, or enough padding has to be put into the shoulder to make up for the difference. You can't just shorten the thing from the bottom and expect a happy ending. In my view, a coat that has a proper left-right balance will almost close on its own without being buttoned, and the sides will hang straight and even, without crossing over or cutting away. Front-back balance problems are more common, and more difficult for tailors to get right. Again, it's not just a matter of getting the length correct; it's a matter of ensuring that the correct amount of length is in the correct place. Just because the front and back appear to line up at the bottom does not necessarily mean that the coat is well balanced. What happens up above is at least as important -- in fact more so. For instance, a guy with "salient blades" (i.e., bulging shoulder blades) needs extra back balance up top, to get around those blades. Similarly, a guy with a prominent tummy needs some front balance in the waist and possibly quarters. And that excess length has to be worked and sewn in the right way so that it contours to the body and doesn't hang there. The most common -- and intractable -- problem is a short back. I probably see more short backs than any other balance problem. This is the number one cause of gaping vents, or vents that fail to close properly. A short back does not have enough cloth up top to make it around the curve of the shoulder blades, and thus the entire back of the coat hikes upward and the lower back (and the vent flap, if there is one) flares out and away from the body. Here is an illustration of a short back (pictures scanned from Clarence Poulin's Tailoring Suits the Professional Way; out of print): Extra length must be added over the blades and only there; the front should not be affected. Long fronts are the yin to a short back's yang. These tend to cut away, to "open" like an upside-down "V" rather than hang straight. See here: Even though the buttoning point is not marked in the illustration, you should be able to see how the quarters are much more open than they should be, and that they coat's buttoning point is falling lower than it should. Attempting to button that coat would force the fronts upward, lift the collar off the back of the neck, and cause the lapels to bow outward above the button. Short fronts, by contrast, lift out and away from the bottoms. Worse, when seen from the front, the quarters cross over: And on long backs, the excess cloth tends to bunch in the small of the back, above the seat, which acts as a sort of "shelf": Beyond this, excellent front-back balance follows the contours of the body. The cloth lies smoothly and almost appears to "adhere" to the body but of course it does not. Excellent front-back balance can especially be seen at the bottoms, from a side view. The cloth should not flare our or kick up but either hang straight or (better, in my opinion) slightly turn inward. One last point, because this tends to get confused. Proper balance is something independent of silhouette and model. That is, for a given client, the balance of his clothes should ideally all be the same whether he chooses DB or SB, 2- or 3-button, high button stance or low button stance, etc. Similarly, balance is balance, whether one prefers a lean, fitted, sculpted cut or whether one is a devotee of drape. As I have argued elsewhere, some of these choices work better with certain body types than with others. Not that such considerations should be dispositive; style is after all about what you like, not what someone else thinks works best for your build. Nonetheless, a perfectly balanced coat in the "wrong" style for you will not necessarily make you look your best. A short, heavy guy in a perfectly balanced DB with a low button stance, floor level peaked lapels, and a huge wrap (crossover) is going to look more like a fireplug than a guy whose DB coat has a narrower wrap, raked up lapels, and a high stance. Balance is fundamental, but it isn't everything.