How To Measure
Take a well-fitting dress shirt, lay the collar flat and measure from center of neck button to beginning of buttonhole.
For suit jackets and sport jackets only, measure over your arms at the highest point of the shoulder blades and the fullest part of arms. If the difference between the chest and the overarm measurement is greater than 7 inches, order the next larger size.
Measure around the fullest part of the chest, keeping tape up under the arms and across the shoulder blades. Keep your arms relaxed.
Measure around waist where you normally wear your pants (measure over shirt, but not over slacks or belt).
With forearm parallel to chest, measure from back center of neck around the elbow to the wrist bone. You can also use a well-fitting shirt, fold at center of shoulder and measure the same as above.