Shoulder fit is the only fit that matters in a coat

There is one measurement on a coat that decides whether you keep it, and it is not the chest, the length or the sleeve. It is the shoulder. Sleeves shorten, side seams come in, hems come up, waists get suppressed and buttons move. A shoulder that is in the wrong place is a rebuild of the entire top half of the garment, which is why tailors quote prices for it that make people laugh. Buy the shoulder and alter the rest.

Where the seam is supposed to sit

On a conventionally cut coat, the shoulder seam should end at the bony point at the outside top of your arm, within about a centimetre either way. Put two fingers on that bone, then look at the seam. If the seam is inboard of it, the coat is too small across the shoulders. If it has run down your upper arm, it is too big.

You can see the error even with the coat done up. Too narrow and the fabric strains into diagonal lines from the shoulder towards the armhole, and the sleeve head puckers. Too wide and a dent or a divot forms just below the shoulder point, where the sleeve head has nothing to sit on, and the whole sleeve hangs with a small collapse in it.

The seam position matters because the shoulder is where the coat hangs from. Get it right and the garment balances: the collar stays against your neck, the fronts hang parallel, the hem is level. Get it wrong and every other problem you notice afterwards is a symptom of this one.

Why it cannot be fixed

Narrowing a coat shoulder means unpicking the lining, taking the sleeve out, removing or re-shaping the shoulder pad and any interfacing, re-cutting the armhole, re-setting the sleeve so it still hangs straight, then putting the lining back. The sleeve head has ease built into it that has already been shrunk to fit a particular armhole, so it will not simply go back into a smaller one.

The cost is a serious fraction of what you paid for a mid-priced coat, and the result depends entirely on the skill of the person doing it. Some tailors will not take the job on a factory coat at all, because the interfacing is fused rather than sewn and does not survive being disturbed.

Widening is worse. There is no spare fabric to widen into. The only route is a different coat.

What can be altered, and roughly how far

Sleeve length: straightforward from the cuff on a plain sleeve, more involved if there are buttons or a tab at the cuff, in which case a good tailor takes length out of the sleeve head instead. Cheap and reliable either way.

Body width: a coat can usually be taken in at the side seams and the centre back seam by a few centimetres in total before the balance starts to complain. The limits are pocket position, the armhole depth, and the point at which the seams have moved so far forward that the silhouette looks wrong from the side. Letting a coat out is limited to whatever seam allowance the factory left, which is rarely generous.

Hem length, waist suppression, darts, button position and belt holes are all routine. So is shortening a collar point or moving a belt loop. None of that is the hard part.

The four tests to run when you have it on

Do it up and put your arms down. The fronts should hang closed without pulling across the chest, and the collar should sit against your neck with no gap behind it. A gap at the back of the collar when the coat is buttoned almost always means the shoulders or the balance are wrong.

Then wrap your arms around yourself as if you were cold, and reach forward as if for a door handle. A coat does not need to be comfortable in a gym, but you should be able to do both without the back seam feeling like it is about to go and without the sleeves riding up to your forearm.

Then put on the thickest thing you intend to wear underneath and repeat. Coats are bought in autumn and worn over knitwear in February. A coat that fits over a shirt and not over a jumper is a coat you will stop wearing.

Buying a coat online, where you cannot do any of that

Measure the shoulders of a coat you already own and like. Lay it flat, face down, and measure in a straight line from the end of one shoulder seam to the end of the other, across the back. That one number is what you compare against the listing, and it is worth more than your chest measurement.

A coat meant to go over a tailored jacket wants roughly two to four centimetres more across the shoulder than the jacket itself. Any less and you will feel the coat gripping the jacket's own shoulder, which is both uncomfortable and visible.

If the listing does not give an across-shoulder measurement, ask for it. We are happy to go and measure a specific size rather than quote a chart, and for a structured shape like The Biker Jacket, which is not on sale yet, the shoulder is the only number worth having.

When the rule does not apply

Drop-shoulder and oversized cuts move the seam deliberately down the arm, so the bony-point test tells you nothing. What you are judging instead is where the seam lands relative to the rest of the design, whether the armhole is deep enough to let you lift your arms, and whether the extra width has made the neck gape.

With an oversized shape such as The Oversized Long Coat, read the measurements rather than trusting the photograph, and expect the sleeve to be long: that is part of the cut, and it is still the cheapest thing to correct.

The other exception is a deliberately soft, unstructured shoulder, where there is no pad and no firm interfacing. These are more forgiving of a near miss because there is nothing rigid to collapse. A sharply built shoulder on a tailored shape like The Suit Trench is the opposite: it shows every millimetre of error, which is precisely why it looks good when it is right.

Questions people actually ask

Can a tailor make a coat's shoulders narrower?

Technically yes, practically it is rarely worth it. The job means removing the lining and sleeve, re-cutting the armhole and re-setting the sleeve, and on a factory coat with fused interfacing many tailors will decline. It usually costs a large fraction of the coat's price.

How do I know if a coat's shoulders fit?

The shoulder seam should end within about a centimetre of the bony point at the top outside of your arm. Diagonal strain lines mean it is too narrow. A dent just below the shoulder, with the sleeve hanging limp, means it is too wide.

What coat measurement should I compare when buying online?

The across-shoulder measurement: lay a coat you already like face down and measure straight from one shoulder seam end to the other. Compare that number to the listing. It matters more than chest size, and a coat worn over a jacket wants two to four centimetres more than the jacket.