How it should fit
This is a matter of taste and a bit subjective. Generally speaking the sleeves should be slim enough to look clean, but not so tight as to cause discomfort under the armpit or at the elbow. Older clients used to a more “generous” shirt cut generally prefer a wider sleeve width. Younger clients looking for a more modern slim fit shirt will prefer the sleeves as trim as possible without causing any discomfort.
How the adjustment works
Widening the Sleeve Width by .25” increases the total circumference of the sleeve at the bicep (1” below the armpit) by .5”.
Adjusting the Sleeve Width also increases the overall circumference of the armhole (lowering the bottom of the armpit). A smaller Sleeve Width will have a correspondingly smaller armhole.
Caution: Slim sleeves can be too tight at the elbow
Decreasing the Sleeve Width will also make the sleeve slightly tighter around the elbow as well, so be careful not to make it too tight. Bend your arm fully with your current fit to make sure you’re not in danger of being uncomfortable at the elbow.
If you want to make the sleeves slimmer around the bicep but they are already dangerously slim around the elbow and forearm, you can usually decrease the sleeve width by .25” and increase the number of pleats in the forearm without creating problems.
Overall sleeve shape and taper
There are a number of ways to adjust the size and shape of a dress shirt sleeve to best fit ones preferences. All of the dimensions below work together in any combination of ways to create your ideal sleeve fit.
Sleeve Width: This dimensions controls the width of the bicep, measured 1″ below the armhole seam.
Cuff Around: Specifies the overall circumference of the shirt’s cuff.
Sleeve Length: The overall length of the sleeve measured from center back, to the shoulder seam, down to the cuff’s end.
Forearm Pleats: Pleats applied to the shirt where the forearm end of the sleeve meets the cuff. Increasing the number of forearm pleats provides more room in the lower half of the sleeve. Decreasing the forearm pleats will reduce the width of the lower half of the sleeve.