How a Shirt or Blouse Should Fit.

Test it in under a minute

Button the shirt and stand side-on to the mirror. The fabric between each button should lie flat across your bust, with no gaps and no creases pulling toward the buttons. Then find where the bust darts or princess seams end. They should point at the fullest part of your bust and stop 2.5 to 5 cm (1 to 2 inches) short of it.

Now move. Reach both arms forward as if you are carrying a box. This is where most shirts fail: the button at bust level pulls open. Sit down and lean forward as if you are at a desk. Raise both arms overhead and check that the sleeves do not drag the whole shirt up and that a tucked hem stays tucked. Finally lean forward and look down. A collar or neckline that falls open at that angle will do the same all day.

If no gap opens and nothing digs in under your arms, the size is right.

What you cannot change later

The bust, shoulders and armholes are set when the shirt is cut. A tailor cannot add fabric at the bust, and moving the shoulder seam is rarely worth it. A dart can sometimes be shortened or moved a little, but the old stitching can leave marks on fine fabric.

What a tailor can do easily: take in the waist at the side seams, add darts at the back for shape, shorten the sleeves and shorten the hem. So buy the size that fits your bust and shoulders, then have the waist brought in. A shirt that fits your waist but gapes at the bust is the wrong size, however well it fits everywhere else.

Ignore the number on the label. Sizes vary between brands, and vanity sizing means the same measurements can be a 6 in one store and a 10 in another. When a brand lists garment measurements, compare its bust measurement with yours. A fitted shirt needs a few centimeters more than your bust, a relaxed one much more.

Fitted, classic and relaxed cuts

A fitted shirt follows your shape with darts or princess seams. Right means a smooth line from bust to waist with enough room to sit and reach. Horizontal lines from your bust toward the side seams mean it is too small, even if it buttons.

A classic, straight-cut shirt has little shaping and more room at the waist. It works tucked into trousers and skirts. Right means the shoulder seams sit at your shoulder bones and any spare fabric gathers at the waist, not at the shoulders or armholes.

Relaxed, boyfriend and oversized shirts are cut wide on purpose, usually with a dropped shoulder. They are meant to be worn loose, half-tucked or open over a top. An oversized shirt is still in proportion: the sleeves end near your wrists or are made to be rolled, and the collar sits at your neck.

A standard shirt bought several sizes up looks different. The shoulder seams sit halfway to your elbows, the armholes drop to your ribs, the collar stands away from your neck and the darts land at your waist. That is too big, not oversized.

When standard sizes don't fit you

Larger bust: size up to fit the bust and have the waist taken in. Look for shirts with closer button spacing, princess seams or a button placed at bust level, and for ranges sized by bust and cup. A hidden snap sewn between the buttons at the fullest point stops small gaps when you move.

Small bust and broad shoulders: buy for the shoulders. Straight cuts with little dart shaping avoid the empty pockets of fabric that a deep dart leaves on a smaller bust.

Full hips: a shirt that fits your bust can pull across your hips when worn untucked. Look for side slits or a curved hem, wear it tucked, or have a tailor open short slits at the sides.

Petite: petite sizes shorten the sleeves, the body and the distance from shoulder to bust point, so darts and waist shaping land in the right place. Regular sizes on a petite frame put the darts too low.

Tall: tall ranges add sleeve and body length. Sizing up adds width, not much length.

Related guides

Pair this with how a blazer should fit and how dress pants should fit. For a shirt you already own, upload a mirror photo to the fit check, or take the fit quiz.