A cuff has to pass over your hand and then stay above it

The problem a cuff exists to solve

Your hand is wider than your wrist. That single fact is the whole design brief. A sleeve end has to be large enough for the hand to pass through, then small enough that it does not slide back down over the hand once you have your arm in, and no fixed circumference can do both.

Everything at the end of a sleeve is a response to that. A buttoned cuff opens to hand width and closes to wrist width. An elastic or ribbed cuff stretches and returns. A wide, unfastened sleeve simply gives up on the second requirement, which is a legitimate choice on a garment where the sleeve is meant to hang.

Once you see the conflict, the mistakes make sense. A cuff buttoned loose enough to slip over the hand while fastened has surrendered the point of being fastened at all, and the shirt will spend the day with its cuff halfway down the palm.

Where the cuff should sit, and the bone that decides it

A shirt cuff belongs at the base of the thumb, resting against the hand when the arm hangs and pulling back a little towards the wrist bone when the elbow bends. That gives roughly the right amount showing beyond a jacket sleeve without the cuff being long enough to swallow the hand.

Sleeve length and cuff depth interact here in a way people often miss. A deep cuff of eight centimetres and a shallow one of five, on sleeves of identical total length, put the button at quite different points on the forearm. The deeper cuff holds the sleeve further up the arm because it is more rigid over a longer stretch.

Bending the elbow consumes sleeve length, which is why a shirt that looks correct with arms down can retreat noticeably when you reach forward. Some of that is unavoidable geometry. A lot of it is a sleeve cut narrow through the forearm, so there is no slack to be borrowed.

Barrel, double and the reason two buttons exist

A barrel cuff is a single layer that wraps and fastens with a button. Many carry two buttons side by side, which is not decoration: it offers two circumferences, roughly a centimetre and a half apart, so the same shirt fits a heavier or lighter wrist. Using the outer one permanently is perfectly reasonable.

A double cuff, folded back on itself and joined by a link through four aligned holes, has no adjustment at all. The fastening passes straight through, so the circumference is exactly what the pattern says. That rigidity is part of why it reads as formal — it cannot be casually loosened, and it presses into a clean, square shape.

Both are still solving the same hand-versus-wrist problem, just with different hardware. And both fail the same way when the opening is cut too small, because the strain lands on the placket slit above the cuff and eventually splits it.

Jacket sleeve buttons are usually a decoration pretending otherwise

The buttons on a tailored jacket cuff are, on most garments, sewn onto a closed sleeve with no buttonholes cut. On more expensive work they are functional, with real holes and a vent that opens. Neither is better in any practical sense; almost nobody undoes them.

Functional buttonholes do have one hard consequence. Once the holes are cut, the sleeve can no longer be shortened from the bottom in the ordinary way, because the buttons and holes would end up at the wrong distance from the hem. The alteration has to be done at the shoulder instead, which is far more involved and considerably dearer.

That is a genuine trade rather than a straightforward upgrade. If a jacket fits at the shoulder and needs a centimetre off the sleeve, sealed cuffs are the convenient option and open ones are the expensive one.

Knitted cuffs are a different mechanism entirely

The ribbed cuff on a sweatshirt or a jumper works by elastic recovery rather than by a fastening. Ribbing is a knit structure of alternating columns that folds accordion-like when relaxed, so it can stretch a long way across its width and pull back afterwards.

It wears out in a specific, recognisable way. Repeated stretching gradually straightens the folds and the yarn loses its ability to return, so the cuff ends up permanently open. Where the rib includes an elastic fibre, that fibre degrades faster than the wool or cotton around it, and the cuff goes slack while the garment is otherwise fine.

Cuffs can be reknitted or replaced, and on a good jumper it is worth doing. On most machine-made sweatshirts the labour costs more than the garment, which is the same unhappy arithmetic that governs almost every repair decision in a modern wardrobe.