Single breasted or double breasted, in plain terms

A single breasted coat has one column of buttons and the fronts meet in the middle. A double breasted coat has two columns, and one front crosses over the other by anything from eight to eighteen centimetres before it fastens. That overlap is the whole difference, and everything else follows from it: how warm the coat is at the chest, how wide it makes you look, how it hangs when it is undone, and how much room there is for a jumper underneath. Neither is more formal than the other in outerwear, whatever is true of suits.

What the overlap does

Two layers of cloth across the whole chest, rather than one, is a real thermal difference. It is the reason the shape exists: naval and military greatcoats were double breasted because the overlap could be buttoned to either side depending on which way the wind was coming, and because a double thickness over the chest is where you most want it.

The overlap also seals. A single breasted coat closes on a line, and in a crosswind that line leaks. A crossed front has no opening on the centre of the body at all.

And it carries width. The buttons sit out towards the sides of the chest, which draws the eye outwards and makes the upper body read broader. This is the effect people mean when they say double breasted is a strong shape.

How each one fits a frame

If you are broad through the chest and shoulders already, a double breasted coat emphasises that, and on a short frame the horizontal line of buttons also cuts the body visually in half. Both of those can be what you want. If they are not, a single breasted front with a long unbroken line of closure is the slimmer, taller reading of the same coat length.

If you are narrow or slight, the opposite applies and double breasted adds substance that a single breasted coat cannot. A slim frame in a big crossed front coat is one of the few places where a deliberately heavy shape flatters rather than swamps.

Height interacts with button position more than with the front type. The lowest button on a double breasted coat sets where the waist appears, and if that point sits below your natural waist the coat shortens your legs. Check the button position against your own torso rather than against the model's.

The Oversized Long Coat is double breasted and cut long, so it does both of those things at once: it widens the chest and sets a low closing line. On a tall frame that reads as a greatcoat. On a short one it reads as a lot of coat, which is covered properly in the piece on buying a long coat when you are short.

Worn open, which is how most coats are worn

A single breasted coat hangs open cleanly. The fronts fall straight, the lapels sit flat, and the shape is the same as when it is buttoned.

A double breasted coat has a problem when it is open: there is a large flap of cloth on each side with nothing holding it, and it tends to swing forward or fold back on itself. Some are drafted to deal with this with a wide lapel that rolls to the waist and sits against the chest. Many are not, and they look unfinished undone.

This is worth looking at in photographs. If a double breasted coat is only ever shown buttoned, there may be a reason. If it is shown open and the lapels lie flat against the body in a clean line down to the waist, it has been cut by somebody who thought about it.

A belted coat sidesteps the question. The Belted Trench can be left hanging, tied, or wrapped without buttoning, and a belt holds the fronts where you put them, which is the real reason belted coats are easy to wear.

Room for layers

A double breasted front is more forgiving over a jumper, because the overlap gives you something to spend. Shift the cross a centimetre or two and the coat still closes, just with slightly less overlap than drawn. A single breasted coat has exactly one closing position and no slack at all.

That said, the chest circumference is set by the pattern, not the number of buttons. A tight double breasted coat is still tight, and the failure shows as the overlap pulling and the lapel standing away rather than as a gap.

Where the extra fabric does cost you is bulk at the waist under a belt or a bag strap, and a little weight. Two layers of a heavy wool across the chest is noticeable in the hand when you pick the coat up.

Reading the buttons

Double breasted coats are described by two numbers: the total buttons and the number that actually fasten. A six by two has six buttons showing and two that do anything, the top pair being decorative. A six by three fastens three ways and sits higher. A four by two is the cleaner, more modern arrangement with less hardware on the chest.

Count the buttonholes rather than the buttons in the photograph. The decorative ones have no hole behind them, and on a coat where they do, the front can be buttoned higher for weather, which is a genuinely useful feature.

On a single breasted coat the thing to read is the button stance: how high the top fastening button sits. A high stance closes the chest and narrows the opening, which is warmer and more formal looking. A low stance shows more of what is underneath and lengthens the torso. The Suit Trench is a single breasted shape that leans on a high stance and a sharp shoulder, which is what makes it read as tailoring rather than as a mac.

And a fly front, where the buttons are hidden behind a placket, is a third option that looks like neither. The Patent Trench buttons to the throat, which gives the long unbroken line a single breasted coat does best.

Which to buy

Buy double breasted if you want the coat to be the garment people notice, if you are often outdoors in wind, if you are slight through the chest and want substance, or if you will mostly wear it done up.

Buy single breasted if you want the coat to work over a suit, if you are already broad, if you want the longest possible vertical line, or if you are honest with yourself that you never fasten a coat.

If you can only own one coat and you live somewhere with a real winter, the double breasted one is the warmer object. If you can only own one coat and you need it to go to work and to dinner and on a train, single breasted is the more adaptable one. That is the whole trade.

Questions people actually ask

Is a double breasted coat warmer?

Yes, meaningfully. The crossed front puts two layers of cloth over the whole chest and leaves no opening on the centre line, so it blocks wind where a single breasted coat closes on a seam that can leak.

Does double breasted make you look bigger?

Across the chest, yes. The buttons sit out towards the sides and draw the eye outwards, and the lowest button sets a horizontal line at the waist. That adds substance to a slight frame and emphasises a broad one.

Can you wear a double breasted coat open?

You can, but it depends on the cut. A coat drafted with a lapel that rolls low and lies flat against the chest looks right undone. One drafted only to be buttoned leaves two loose flaps that swing forward.

What does six by two mean on a coat?

Six buttons visible on the front, two of which actually fasten. The top pair is decorative unless there are buttonholes behind them. A six by three fastens three ways and closes higher up the chest.