An ill-fitting suit can make you look sloppy, so you naturally want to take proper measurements before you buy a suit. Men's suit sizes are based on height and chest measurements, with regular suits featuring a 6-inch "drop" or difference between the chest and waist of the suit. Portly men don't have as big of a difference between the chest and waist size, so the drop on a portly suit is 4 inches. Measure yourself to get the right suit fit.
Wrap the tape measure around your chest. This should be at the widest part of your chest. Make sure that the tape measure is straight and not twisted. Make a note of the measurement.
Take the over-arm measurement by measuring your chest again, but this time by wrapping the tape measure around both of your arms. You'll need a friend or family member to take this measurement.
Subtract seven from the over-arm measurement.
Compare your adjusted over-arm measurement with the chest measurement. Use the larger of the two, which represents your suit jacket size.
Measure your waist at the top of your hip bones, usually about 1 or 2 inches below your belly button. It is not the measurement of your hips under your belly.
Use your tape measure to find your inseam. The inseam is the measurement from the crotch of your pants to the desired length, along the inside of your leg. Again, you might need someone else to help with this.
Use your height to further refine suit sizing. Your height will affect the size of the suit, because taller men have a longer torso. In general, men who are 5 feet 4 inches tall or shorter will wear the extra-short size. Those 5 feet 5 inches to 5 feet 7 inches tall wear a short. Those 5 feet 8 inches to 5 feet 11 inches tall wear a regular. Those 6 feet tall to 6 feet 2 inches tall wear a long, and those 6 feet 3 inches and taller wear an extra-long size.