How to determine my shirt size?

Chest: Measure around the fullest part of the chest/bust area. The tape should be snug, under the arms and around the shoulder blades.

Waist: Measure around the waist, at the natural waistline, over shirt (not over slacks).

Sleeve Length: Measure the distance from where your spine meets the base of your neck to your shoulder seam.
Then, with your elbow slightly bent, measure from shoulder seam to wrist.
The sum of these two numbers is your sleeve length.

Neck: Measure around your neck, keeping two fingers between the measuring tape and your neck.