Fitting a suit can be a daunting task, especially if you are an unusual sized guy. A hundred years ago or so, most people had clothes made, so finding your size was as straightforward as getting measured. However, now, people buy clothes off the rack, which are sized for the average person. Unfortunately, most people are not the average.
Buying a suit is an especially delicate situation, for several reasons. First, similarly to uniforms or military style clothing, the cut of a suit is almost an official standard. Unlike other clothing where different styles may have a slightly different cut, with a suit there are certain proportions you generally want to achieve. Secondly, a suit is usually far more expensive than anything else you’ll buy, meaning that the decision needs to be made well, as consequences are more dire.
Fortunately, a suit can usually be altered fairly easily. Some parts can be changed more easily (and inexpensively) than others. The shoulders are the part of the suit that are hardest to change. Fortunately, for most men, their shoulder size doesn’t change much, and sees far less fluctuation than other areas, such as the midsection. Also, changing the shoulders requires a similar amount of effort (and costs about as much) as creating the jacket in the first place. So, when fitting a coat, get one that has perfectly-fitting shoulders.
Sleeve length is the second detail. The jacket should have short enough sleeves that a half to three quarters of an inch of shirt cuff is visible when the man’s arms are hanging at his sides. If the jacket sleeves are longer than that, and the shirt cuff doesn’t show, it gives the illusion that the man is a boy, borrowing his father’s suit coat. The sleeves can be shortened to some degree, but if too much fabric is taken up, the buttons on the side will be in the wrong place, so get a jacket with sleeves that are close to the right length if possible.
Stomach/trunk width is another crucial area. If a man is quite athletically built, this area will probably be far too roomy. A suit is designed with a drop of 6 inches, meaning that the shoulders are 6 inches bigger than the waist of the pants (and the suit waist, which corresponds to the pants). Of course, many men are not a six inch drop, and may need the waist of the suit coat, and the pants taken in or out.
The pants may also need to be taken in, both in the waist or in the legs. Most suit pants are cut roomy, since adding fabric is far harder than removing it. However, if too much fabric must be removed at the waist (such as accounting for a large drop), the pockets at the back can move too close together. If this is the case, getting a separate pair of pants is probably the best option, although this can be difficult.