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 circumference of the sleeve at the bicep (1” below the armpit) by .5”.
Adjusting the sleeve width also increases the size of the armhole (lowering the bottom of the armpit). A smaller sleeve width will have a correspondingly smaller armhole.
Overall, the sleeve circumference at the center of the arm is determined by the cuff size* and the sleeve width at the bicep. Increasing the sleeve width .5” will increase the sleeve width at the elbow by about .25”. Selecting between the 1-pleat, 2-pleat (recommended), and 3-pleat forearm can also be used to adjust the sleeve width at the elbow. Read more on using forearm pleats to adjust the lower sleeve circumference here.
*Note: We do not recommend adjusting the cuff size to increase the sleeve width at the elbow. Small (.25″ – .5″) increases in cuff size will have little to no measurable affect on the sleeve’s elbow width.
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.