A long sleeve runs the full arm and ends at the wrist bone, the knob on the outside of the wrist. Tailoring builds a hierarchy on that point. A shirt cuff closes at the bone, and its jacket is cut fractionally shorter. That way a quarter to a half inch of shirt cuff shows past the jacket sleeve, the classic signal that both garments fit.
Full coverage is what the length trades in. Warmth rises with every covered inch, and sun stays off the forearm. Formality follows almost automatically, since suits, dress shirts and most formal knitwear assume the full sleeve. Codes that specify covered arms mean this. The wrist test is simple and worth running every time you buy. Let both arms hang relaxed and confirm the hem touches the wrist bone without burying the hand. Arms differ enough that many people wear a different sleeve length than their chest size predicts.
Length errors are the most visible fit errors on the upper body, and also the most fixable. A sleeve puddling past the wrist reads borrowed, and a hem riding above the bone reads outgrown. Yet shortening a sleeve is among the cheapest alterations a tailor performs. The exception is jackets with working buttonholes at the cuff, where the surgery happens at the shoulder and the price multiplies. Buy for the shoulders and chest, then let the sleeve be corrected.
In photos
Long Sleeve on real products
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