For Ready To Wear Shirts each Collar Size has a corresponding Chest size and Sleeve length. When a new shirt is delivered the actual collar measurement will be up to 1/2" (1.3cm) larger. This allows for shrinkage, which happens to all quality cotton during its first few washes. The sizes stated below for the chest and sleeve measurements are the actual garment measurements. We recommend 6” to 8” (15.2cm to 20.3cm) over a customer’s chest measurement to allow for freedom of movement.