First measure the collar size. Place the tape measure around your neck and add half an inch to get the most comfortable fit.
Start from the top of the center back, just below the collar and measure to your shoulder. Then measure from your shoulder to your wrist bone.
Run the measuring tape around the widest part of your chest, just below your armpits.
Place the measuring tape around your natural waistline which is the narrowest part of your waist.