HOW TO MEASURE FOR CORRECT SHIRT SIZE
Measure around your neck just below your Adam's apple. Add a half-inch to the measurement for comfort. This is your neck size. It is the first number in the sizing of men's shirts. Then have someone measure one of your arms, with it hanging straight at your side. Measure from the center back of your neck, over the top of your shoulder and down to your wrist. This measurement is the next number in the sizing. For comfortable men's shirts, be sure that the armholes and arms don't fit too snugly. If you have a shirt that fits you very well, you can also measure it to determine your size if it's not tagged inside the shirt.