Most people judge a jacket by the overall impression: it feels good, or it feels tight. That is a poor measure, because a jacket that is too wide feels comfortable and still looks wrong. It is more reliable to look at the places where a jacket is actually built. There are six of them, and they matter in this order.
1. The shoulder
The shoulder seam should end where your shoulder ends – at the edge where it turns into the arm. If it ends earlier, the jacket pulls with every movement. If it ends later, a small dent appears below the seam, often a hand's width down: the padding is carrying, the shoulder is not.
Check this in profile, not from the front. From the front almost every shoulder looks right. The shoulder is the most important of the six – and the only one where a later alteration is costly and rarely truly good.
2. The collar
The jacket collar should sit against the shirt collar, with no gap and no fold. A gap between the two – the classic collar gap – is the most common sign that an off-the-rack jacket does not match the wearer's posture.
Stand up straight, let your arms hang, and look over your shoulder into the mirror. The collar must not lift even when you bring your arms forward.
3. The sleeves
The jacket sleeve ends where the hand begins – at the base of the thumb. About one to one and a half centimetres of shirt cuff should show. Less looks stunted, more untidy.
One detail matters here: arms are rarely the same length. A properly made jacket takes that into account and has two sleeves of slightly different length. Nobody notices that. The opposite, people do notice.
4. The fastened button
Fasten the top button (on a two-button jacket) and look at the area around it. If folds radiate from the button in the shape of an X, the jacket is too tight at the waist. If the cloth falls flat with no tension at all, it is usually too wide.
A well-fitting jacket shows nothing at this point – neither folds nor emptiness. That sounds like a weak criterion, but it is the most reliable of them all.
5. The length
The classic rule: the jacket covers the seat. The second is more practical – let your arms hang and curl your fingers. The hem should sit roughly in the cup of your hand.
Both rules are guides, not laws. Anyone very tall or very short will, in proportion, wear it slightly shorter or longer. What matters is that the jacket and the length of the leg stand in a sensible relation to each other.
6. And what can still be changed?
This is the question that saves the most money – asked before buying. Broadly:
- Sleeve length: almost always possible, even on jackets with working cuff buttons (more involved then, because the change is made from the shoulder).
- Waist: taking it in works well, letting it out only as far as the seam allowance goes.
- Length: shortening is possible, but it changes how pockets and button height relate to the hem – in small steps only.
- Collar: can be corrected if the gap comes from the making and not from the posture.
- Shoulder: alterable in theory, in practice the most expensive and most delicate operation. A jacket whose shoulder does not fit should not be bought.
Having a suit made to measure avoids this list altogether – there, all six places are calculated for one person instead of an average. Even then it pays to look closely at the fitting. A fitting is not a formality; it is the moment measurements turn into a fit.