Quick Answer: The traditional tailoring guideline is about 1 to 1.5 centimetres of shirt cuff showing beyond the blazer sleeve, roughly a quarter to half an inch. To get there, the blazer sleeve should end around the wrist bone and the shirt cuff should reach the point where your wrist meets your hand. If no cuff shows, the blazer sleeve is too long or the shirt sleeve is too short, and the blazer is usually the one to fix.

You put on a good blazer over a good shirt and something still looks unfinished. Nothing is creased. Nothing is too tight. The colours are fine.

Then you glance down at your wrists. On one side the shirt has vanished completely. On the other, half the cuff is sticking out like it’s trying to leave.

How much shirt cuff should show under a blazer?

About 1 to 1.5 centimetres, seen with your arms relaxed at your sides. That’s the long-standing convention in tailoring, and it carries across to women’s blazers without any change.

The thin band of shirt does two jobs. It frames the hand with a line of lighter colour, in the same way a collar frames the face. It also tells the eye that both sleeves are the right length, which is why its absence is so easy to notice even when you can’t say what’s wrong.

Treat the number as a guide. A little less looks quiet and modern. A little more, up to about 2 centimetres, suits a shirt with a deep or decorative cuff. Past that, the blazer starts to look as if it has shrunk.

Where should a blazer sleeve end, and where should the shirt cuff end?

The blazer sleeve should finish at about the wrist bone, the small bump on the outer side of your wrist. The shirt cuff should run slightly further, to the point where the wrist meets the base of the hand.

Check it like this:

• Stand in front of a mirror with your arms hanging naturally. Don’t straighten or lift them.
• Look at the outer wrist. The blazer hem should be level with the wrist bone or just covering it.
• The buttoned shirt cuff should sit snugly enough that it doesn’t slide down over your hand.

That last point matters more than people think. A cuff that’s too loose slips towards the knuckles and shows far more than it should. A cuff that fits the wrist stays put, and the amount on show stays the same all day.

When you bend your arm, more cuff will appear. That’s normal. The measurement only applies with the arm down.

Why does no cuff show even though both pieces are your size?

Three usual suspects: the blazer, the shirt, or the shoulders.

Most often, the blazer sleeve is simply long for your arm. Ready-made jackets are cut for an average arm length in each size, and plenty of people fall a centimetre or two either side of it.

Sometimes the shirt is the problem. If the shirt sleeve stops short of the base of the hand, or the cuff is so wide that it rides up inside the blazer, there’s nothing left to show.

The third cause is the one that surprises people: the shoulders. If the blazer is too wide across the shoulders, the shoulder seam drops down your upper arm and takes the whole sleeve with it. The sleeve looks too long, but shortening it only treats the symptom. Check that the shoulder seam sits at the edge of your shoulder before you alter anything else.

5 Mistakes Everyone Makes With Blazer Sleeves

1. Checking the length with arms raised. Reaching forward pulls any sleeve up. Judge it standing, arms down.

2. Leaving the sleeves long so they’ll cover the wrist when you move. A sleeve that covers the wrist when you reach will cover half your hand when you stand still.

3. Pulling the shirt cuff down by hand. It slides back within minutes. If you need to tug, one of the two sleeves is the wrong length.

4. Wearing a watch that fights the cuff. A thick watch under a close-fitting cuff pushes the shirt sleeve up on one side, so the two wrists don’t match. Wear it slightly looser, or choose a slimmer watch with fitted cuffs.

5. Assuming all sleeves can be altered the same way. They can’t, and the difference comes down to the buttons.

Can a tailor shorten or lengthen blazer sleeves?

Shortening is one of the most common blazer alterations. If the cuff buttons are decorative, with no real buttonholes cut through the fabric, a tailor can take the sleeve up from the cuff and move the buttons. A change of 1 to 3 centimetres is routine.

Working buttonholes make it harder. They can’t be moved, so any real change in length has to be made from the shoulder end of the sleeve. That’s a bigger and more expensive job, and not every tailor will take it on. Check the cuffs before you buy a blazer that needs shortening.

Lengthening depends on what’s hidden inside. Turn the cuff back and look at the fabric folded up inside the hem. That allowance is all a tailor has to work with, often 2 to 4 centimetres, and letting it down can leave a faint line on some cloths where the old fold was.

If the blazer is right and the shirt is short, replacing the shirt is nearly always cheaper than altering a jacket.

What if you wear a knit or a T-shirt under your blazer?

Then the rule changes, because there’s no cuff to show. With a fine-gauge jumper or a turtleneck, either let a centimetre of knit cuff show in the same way, or keep the knit sleeve fully inside the blazer. Both look deliberate. A thick ribbed cuff bunched at the blazer hem doesn’t.

With a T-shirt, the blazer sleeve stands alone, so its length matters even more. Wrist bone is still the target.

Autumn is when this comes up most, as shirts give way to knitwear under the same jackets. If your blazers were altered to show a shirt cuff, they’ll sit correctly over a knit as well, since the sleeve length is set against your wrist and not against the shirt.

FAQ: Blazer Sleeve Questions, Answered

Is it wrong if no shirt cuff shows under a blazer?

It isn’t wrong, and nobody will stop you in the street. It does make the sleeves look slightly too long, and the outfit loses a small detail that helps a classic blazer look tailored.

Should a blazer sleeve cover the wrist bone?

It should end at about the wrist bone, either just touching it or just covering it. If it reaches the base of your thumb when your arms are relaxed, it’s too long.

How much does it cost to shorten blazer sleeves?

It varies by city and by tailor. Sleeves with decorative buttons are a standard, moderately priced alteration, while sleeves with working buttonholes or a lined vent cost more. Ask for a quote before leaving the jacket.

TL;DR:

• Aim for about 1 to 1.5 centimetres of shirt cuff beyond the blazer sleeve, arms relaxed.
• Blazer sleeve to the wrist bone, shirt cuff to where the wrist meets the hand.
• If no cuff shows, check the shoulder fit first, then the blazer sleeve, then the shirt.
• Decorative cuff buttons make shortening easy; working buttonholes make it harder and pricier.

It’s a small strip of fabric, and most people will never consciously notice it. They’ll just think the blazer fits you well, and that’s the whole reason classic pieces are worth getting right.