The rule, explained from the cut
Suit button rules: which button, and why the rule exists
The short answer: the bottom button never fastens. On a two-button jacket you fasten the top one, on a three-button the middle one, on a one-button the only one, and when you sit down you undo all of it. The long answer is the interesting one, because it explains why the rule exists at all: below the waist the fronts are deliberately cut to spring apart over the hips. Fasten the bottom button and you close that allowance, which puts a horizontal crease straight across the hips. This is not a question of taste. It is a cut you are working against. We cut in Shanghai, and a stretched bottom buttonhole is one of the few things that tells you how a jacket was worn.
What stays fastened and what does not, by garment
| Standing | Seated | What happens if you do it differently | |
|---|---|---|---|
| Jacket, one button | Fastened | Undone | Sitting fastened loads that one button and stretches the buttonhole over time |
| Jacket, two buttons | Top fastened, bottom open | Both open | Both fastened puts a horizontal crease across the hips, where the fronts are meant to spring apart |
| Jacket, three buttons | Middle always, top optional, bottom never | All open | The bottom one distorts the skirt exactly as it does on a two-button |
| Waistcoat | All but the bottom one | Same; a waistcoat is not undone | Fastening the bottom makes the waistcoat ride up and stand away from the trouser waistband when seated |
| Double-breasted | Fastened, including the inner jigger | Staying fastened is the exception here; open, it hangs apart | Worn open, a double-breasted jacket hangs crooked because only the inner button holds it in balance |
These are conventional tailoring rules, not house rules. The reason behind all of them is the same: fasten only where the cut expects it.
Why the cut makes the rule
Five terms that turn a rule of manners into a technical one.
- Skirt
- The part of the jacket below the waist. It is cut so the two fronts separate there and leave room over hips and seat. That is exactly why the bottom button sits where it is never meant to close: it is a design element, not a fastening.
- Waist suppression
- The shaping that brings a jacket in at its narrowest point. The fastening button sits at or just above it, because that is where the cloth works least against the body. A button below it pulls against the hip and throws a crease.
- Jigger (inner button)
- The hidden button inside a double-breasted jacket that holds the under-front in place. Without it the overlapping side sags. It is the reason a double-breasted jacket stays fastened, seated included, while a single-breasted one is opened.
- Three roll two
- A three-button jacket whose lapel rolls softly over the top button so it sits half hidden. It is worn like a two-button: middle fastened, top left under the lapel. Unrolling it to fasten the top button presses that roll flat.
- Sleeve buttons
- The buttons at the cuff. On most jackets they are decorative and do not open; on more elaborate ones the buttonholes are real. Leaving one undone to show that they work is a fashion, not a rule. You do nothing wrong by doing it, and you prove nothing either.
Common questions
Which button do you fasten on a suit?
On a two-button jacket, the top one. On a three-button, the middle one. On a one-button, the only one. The bottom button stays open in all three cases, without exception. When you sit, undo the fastened one too and do it back up when you stand. The only suit that stays fastened is a double-breasted.
Why is the bottom button left open?
Because below the waist the fronts are deliberately cut to separate and leave room over the hips. Close them there and you shut that allowance, which gives you a horizontal crease across the hips and a load sitting on the buttonhole. The story about an English king whose stomach was in the way gets told a lot and is hard to verify. The cut is easy to verify: lay the jacket flat and look at how the edges fall away from each other below the waist.
Should you unbutton a jacket when sitting?
Yes, every time. Sitting fastened puts the whole load on one button and one buttonhole, at precisely the moment your body gets several centimetres wider. After a few hundred repetitions it shows: the buttonhole is stretched and the chest carries a crease that pressing will not take out. Undo it as you sit, do it up as you stand.
Which buttons do you fasten on a waistcoat?
All of them except the bottom one. The reason is the same as on the jacket: the lower edge of a waistcoat is cut to sit over the trouser waistband and needs room to move there. Fastened, it rides up and stands away from the waistband when you sit. A waistcoat also stays closed when seated, unlike the jacket.
How do you wear a double-breasted jacket?
Fastened, and fastened while seated too. That is the exception to everything else on this page. A double-breasted jacket is held in balance by an inner button called the jigger; worn open, the overlapping side sags and the fronts hang crooked. If you want to open it the moment you sit down, a single-breasted jacket is the more suitable garment.
What about a four or six button jacket?
On a single-breasted jacket with four buttons in a row we would advise against it, and that is a recommendation rather than a matter of taste: four button positions push the top one so high that the lapel goes short and the jacket reads boxy. Six buttons almost always means a double-breasted, where two or three are decorative and only one actually fastens. Count the buttonholes there, not the buttons.
A jacket whose cut explains the rule
We make made-to-measure suits in full or half canvas from premium European cloth, from a single piece, in about 14 to 20 working days, factory-direct from our Shanghai atelier.