How Long Should a Suit Jacket Be? Length Rules That Actually Work

Jacket length is an easy fit point to get wrong without noticing. A jacket a little too short makes a grown man look as if he has outgrown his suit; one a little too long makes his legs disappear. So how long should a suit jacket be? Long enough to cover your seat, and in proportion to your body. The popular finger rules help, but none of them works for everyone.

How long should a suit jacket be? The short answer

A classic suit jacket should cover your seat completely. From there, two checks fine-tune the length: the hem should fall around your knuckles or the middle of your thumb with your arms relaxed, and the back length should be roughly half the distance from the base of the collar to the floor. When the checks disagree, the seat rule wins.

Rule 1: Should a suit jacket cover your seat?

Yes. A classic suit jacket should cover your seat, and this is the most dependable of the three rules. It works because it is tied to your own body rather than to your arms or a formula. A jacket that covers the seat closes the line between the jacket and trousers neatly, keeps the vents hanging straight and gives the suit its traditional balance.

Check it side-on in a mirror, standing naturally with your weight on both feet. The hem should sit just below the curve of your seat, not on the curve itself. A jacket that ends exactly at the fullest point of the seat looks short when you move, because the hem rides up over it.

Rule 2: The knuckle or thumb check

With your arms relaxed at your sides, the hem of a well-proportioned jacket usually falls around your knuckles or the middle of your thumb. A variant says you should be able to curl your fingers under the hem. It is the most quoted jacket length rule because it needs no tape measure.

It is a guide, not a law. Arm length varies a great deal from man to man, so the rule measures your arms as much as your jacket. A man with long arms who follows it will choose a jacket that is too short at the back; a man with short arms will end up in one that is too long. Use it as a quick check, then confirm with the seat rule.

Rule 3: Half the distance from collar to floor

Many tailors set jacket length by proportion: the back length, measured from the seam where the collar joins the jacket at the back of the neck down to the hem, is roughly half the distance from that point to the floor. The rule ties length to your height, which is why it is the basis of most tailors' first estimate.

To check it, have someone measure from the base of your collar (the prominent bone at the back of your neck) to the floor while you stand in shoes, then halve the figure. Compare it with the back length of a jacket you own, measured down the center back seam from the collar seam to the hem.

The weakness of the rule is that it treats everyone as having average proportions. A man with a long torso and shorter legs may need a slightly shorter jacket than the rule suggests, to leave more leg showing. A man with long legs and a short torso can carry a little more length. This is where the seat rule acts as the floor: whatever the proportions, the seat stays covered.

Is my suit jacket too short or too long?

Your jacket is too short if any part of your seat shows from the side, if the vents splay open over your seat, or if your trouser waistband and a triangle of shirt show below the fastened button. It is too long if the hem falls well past the seat toward mid-thigh, if your legs look short in a full-length mirror, or if the jacket starts to read as a coat.

Length also has to be level. Seen from the side, the hem should run parallel to the floor. A hem that kicks up at the back usually means the jacket is short in the back for your posture; one that dips at the back means the opposite. A tailor calls this the jacket's balance, and it is checked alongside length at every fitting.

How long should a jacket be for short men?

A short man's jacket should cover the seat and no more. That keeps as much leg in view as possible, which makes you look taller, while keeping the jacket in proportion. Short sizes (marked S) exist for exactly this reason: they cut the body and the sleeves shorter than a regular of the same chest size.

Resist going shorter than the seat. A cropped jacket on a short man makes the torso look small and the suit look outgrown. Pair a seat-length jacket with trousers that sit at or near the natural waist and with a quarter or no break at the hem, so the leg line runs unbroken; the options are set out in trouser break explained.

And for tall men?

Tall men most often have the opposite problem: regular sizes are too short in both the body and the sleeves. Long (L) and extra long (XL) sizes add length to both. If you are between regular and long, choose by whether the jacket covers your seat and whether the sleeves reach your wrists, not by your height alone. The suit size chart gives the usual height ranges for each length.

Details that change how long a jacket looks

• Button position: a fastened button set below the navel lengthens the torso and shortens the legs, which makes a long jacket look longer still.
• Front quarters: fronts that curve away sharply below the button show more trouser and make the jacket read shorter; straighter, closed fronts make it read longer.
• Trouser rise: trousers that sit low on the hips leave a gap below the button, which makes even a correct jacket look short. Higher-rise trousers close it.
• Contrast: a jacket and trousers in different colors make the jacket hem a visible line, so its length shows more than on a matching suit.

Can a suit jacket be shortened or lengthened?

A suit jacket can be shortened a little, usually by about 1 inch (2.5 cm), but it can rarely be lengthened. Shortening is harder than it sounds: the tailor has to take off the lining at the hem, recut and press the hem, shorten the vents and rebalance the front. Go further than about an inch and the hip pockets end up too close to the hem, the vents look stubby and the button looks low on the jacket.

Lengthening depends on spare fabric turned up inside the hem, and ready-to-wear jackets have little or none. Even where there is some, the old hem crease can leave a visible line. If a jacket is too short, try the long version of the same size or a different brand. Which other alterations are realistic is covered in what a tailor can and can't alter.

How a tailor decides on jacket length

A bespoke tailor does not pick a length from a chart. They start from the proportion rule, then adjust for your build: the length of your torso against your legs, the curve of your seat, your posture and the style of the house. The length is then checked on your body at the first fitting, when the jacket is still loosely tacked together and the hem can be moved freely.

Length is one of seven fit checks on a jacket. The others, from collar to sleeve, are in how a suit jacket should fit, and the whole suit is covered in how a suit should fit. If you are buying ready-to-wear, start with the right length label, then let a tailor handle the details.

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