How the sleeve length should fit
With your arms hanging relaxed at your sides and the cuffs of the shirt unbuttoned, the sleeves should come down to the center of the back of your hand (or the first knuckle of your thumb). This may seem too long for some folks, however, we find this works very well when the cuffs are also sized appropriately to the wrists. This way, when the cuffs are buttoned they will prevent the cuff from sliding too far over your hand. This extra length will allow you to bend and raise your arms without the cuff sliding up over your forearm.
How the measurement works
The sleeve length is measured from the center back of the neck, just below the collar, over the shoulder and down to the end of the cuff. This is an industry standard way of measuring the sleeve length. Some other shirt makers will specify the sleeve length just from the end of the shoulder to the end of the cuff, so be sure you are not confused by this. With our method of specifying the sleeve length, it is independent of the shoulder (yoke) width, so you don’t have to worry about how adjusting the shoulder width will effect the sleeve length.
We try to account for shrinkage with how long we cut the sleeves, so a 34” sleeve should measure 34.5” right out of the box. If the sleeves seem too long consider first that they will shrink with the first few washings. If they seem too short, consider adding 0.5” in addition to the amount you think they are too short.