Suit jacket sleeves should work with the shirt cuffs and the intended silhouette. Check them with arms relaxed and during normal movement. A small visible shirt cuff is a common styling preference, but the appropriate amount depends on the shirt and jacket.
Fit the shirt before judging the jacket
Wear the dress shirt you plan to use, with cuffs fastened as normal. If the shirt sleeve is too long or its cuff slides over the hand, it can make a correctly fitted jacket seem short. Correct that reference before deciding on an alteration.
Stand naturally and compare both wrists. Slight differences in posture or arm length can require separate adjustments. Also bend your elbows and reach forward so you understand how the sleeves behave outside a posed photograph.
Inspect the alteration constraints
Check whether cuff buttons are decorative or working. Working buttonholes may limit shortening from the cuff. A tailor may propose another approach depending on sleeve construction. Ask how button spacing and sleeve width will look afterward.
Agree the finished length while wearing the normal shirt, not a temporary substitute. Mark each sleeve separately if needed. Recheck with the jacket buttoned and unbuttoned because the body position can change the sleeve's apparent hang.
Should sleeves cover the whole hand?
That is generally an awkward reference for tailored dress wear, but do not correct it by guessing a fixed number to remove. Measure the actual fitting requirement. For bulk uniforms, specify the measuring endpoints and acceptable variation so the approved sample becomes a useful reference.
Related reading
Agreeing jacket measurement methods and tolerances. For another useful reference, see Wearing a polo shirt with a blazer.
