Measure around the middle of your neck (at the Adam's apple) keeping the tape a bit loose.
Measure under your arms around the fullest part of your chest.
Bend your elbow 90 degrees and place your hand on your hip. Hold the tape at the center of your neck. Measure across your shoulder to your elbow and down to your wrist. The total length is your sleeve length.
A slimmer fit through the chest, arms and body. Wear in your usual size for a sharper, more fitted look.
Relaxed through the chest, arms and body for your total comfort.