Cotton weight in ounces, and what each one feels like

T-shirt cloth is sold by weight, and American listings give that weight in ounces per square yard while the rest of the world uses grams per square metre. The numbers describe the same thing and neither tells you what the shirt will feel like on its own, because a light cloth made from good yarn beats a heavy one made from bad yarn in every respect except opacity. Still, the number is the most specific piece of information most listings give you, so it is worth knowing what each band means in the hand, and what it predicts about drape, see-through and how the shirt ages.

The two units, and the conversion

Ounces per square yard is the American convention and grams per square metre is everywhere else. One ounce per square yard is about 34 grams per square metre, so multiply ounces by 34 to get gsm, or divide gsm by 34 to go the other way.

That means 4.2oz is roughly 145gsm, 5.3oz about 180gsm, 6oz about 200gsm and 7oz about 240gsm. Those four numbers cover almost every printed t-shirt sold.

Be slightly careful with American listings, because some give ounces per linear yard of a fixed width roll rather than per square yard, and the two are not the same number. If a weight looks implausibly high for a t-shirt, that is usually why.

The only honest use of the figure is comparison. A 5.3oz shirt is heavier than a 4.2oz shirt from the same maker. A 5.3oz shirt from one factory and a 5.3oz shirt from another can feel completely different.

What each band feels like

Around 4oz to 4.5oz, or 135gsm to 155gsm, is a light summer jersey. It drapes close to the body, it is cool, it is slightly see-through in white and pale colours, and it is the weight that goes soft fastest and thins at the shoulders first. Fashion tees and women's fitted tees live here.

Around 5oz to 5.5oz, or 170gsm to 190gsm, is the standard. This is what most printed t-shirts are, because it is opaque enough in any colour, holds a print well, and survives repeated washing without losing shape. If a listing does not state a weight, assume it is in this band.

Around 6oz to 6.5oz, or 200gsm to 220gsm, is a heavy tee. It hangs rather than clings, it holds a boxy cut, the hem stays where it is put, and it feels substantial in the hand. It is also warmer, slower to dry, and it takes several washes to soften.

Above 7oz, or 240gsm, you are into the heavyweight and boxy tees that behave almost like a light sweatshirt. They are excellent objects and they are not summer garments.

What weight predicts, and what it does not

It predicts opacity reliably. If you want a white or pale shirt that is not translucent, weight is the number to read, and 5.3oz is about where that problem stops.

It predicts drape. Heavier cloth has more mass per area and falls in larger, slower folds, which is why a boxy cut needs weight behind it. A boxy pattern in light jersey collapses and looks like a shirt a size too big.

It predicts warmth and drying time, in the obvious direction.

It does not predict softness, durability or how well the shirt keeps its shape. Those are set by the yarn and the knit: how the cotton was spun, how long the staple fibres are, how tightly the fabric was knitted and whether it was pre shrunk. A heavy shirt made from coarse carded yarn is rough, and it will pill. A light shirt made from combed ringspun yarn is smooth and keeps looking good much longer.

The yarn, which matters more than the number

Carded or open end cotton is spun quickly from fibres that have been cleaned but not aligned, which leaves short ends sticking out of the yarn. It is cheap, it feels slightly rough, and those loose ends are what later roll into pills.

Ringspun cotton is twisted continuously as it is spun, which wraps the fibres around each other into a finer, stronger, smoother yarn. Combed ringspun goes a step further and removes the shortest fibres before spinning, which is where the genuinely soft t-shirts come from.

The practical result is that a 4.3oz combed ringspun tee feels better against the skin than a 6oz carded one, while the 6oz is the more opaque and more structured garment. They are answering different questions.

If a listing gives you a weight and says nothing about the yarn, the yarn is probably carded. Makers who pay for combed ringspun say so, because it is one of the few specifications a customer will pay more for.

Weight and printing

A heavier knit has a slightly more textured surface and more loft, so it absorbs a touch more ink and softens the very finest lines. A light smooth jersey holds hairline detail best. The difference is small on a tee and much larger on fleece, which is covered in the piece on choosing between a tee and a crewneck.

Weight also changes how a print moves. A print on a light stretchy jersey is flexed more often and harder than the same print on a heavy stable one, so on a thin shirt the ink deposit needs to be thinner and more flexible. This is one of the quiet reasons heavyweight tees hold prints well.

And weight affects how a design reads. A heavy boxy tee hangs away from the body, which keeps a large chest print flat and legible. On a light clingy shirt the same print follows the body and distorts. A large central drawing and a wide composition across the chest both want cloth with enough body to hold the shape still.

Which weight to buy

Buy light if you want something cool and close fitting, if you layer it under things, or if you are buying for somewhere hot. Accept that it will go thin at the shoulders sooner and that pale colours will be slightly sheer.

Buy the standard middle band if you want one printed shirt to wear all year and do not want to think about it. There is a reason it is the default.

Buy heavy if you want the shirt to hold a boxy shape, if you wear tees as an outer layer in cool weather, or if you want an object that reads as substantial. A simple graphic on heavy cloth is one of the few garments that improves as it fades.

And if you want warmth rather than weight, stop looking at jersey and look at fleece. A crewneck is a different construction with a brushed inner face, not a thick t-shirt, and no weight of jersey gets you to the same place.

Shrinkage, which the weight does not tell you

Cotton jersey shrinks mostly in length, and mostly on the first hot wash. An untreated cotton tee can lose three to five percent of its length, which on a shirt with a 71cm body is two to three and a half centimetres: enough to turn a good length into a short one.

Pre shrunk, ring spun and compacted cloth has already been through a controlled shrinking process, and it will move perhaps one or two percent. The label words to look for are pre shrunk or compacted. If neither appears, assume it will shrink.

The way to avoid finding out is to wash cold and line dry, which is what a printed shirt wants anyway. Heat is what causes both shrinkage and print damage, and avoiding it solves both problems at once.

Questions people actually ask

How do you convert oz to gsm for t-shirts?

Multiply ounces per square yard by about 34. So 4.2oz is roughly 145gsm, 5.3oz about 180gsm, 6oz about 200gsm and 7oz about 240gsm. Divide gsm by 34 to go the other way.

Is a heavier t-shirt better quality?

Not necessarily. Weight predicts opacity, drape and warmth. Softness, pilling and how long a shirt keeps its shape are set by the yarn: a light combed ringspun tee feels and ages better than a heavy carded one.

What is a good weight for a printed t-shirt?

Around 5oz to 5.5oz, or 170gsm to 190gsm, which is the standard band. It is opaque in any colour, stable enough to hold a print flat and not too warm to wear most of the year.

What does ringspun cotton mean?

The yarn was twisted continuously as it was spun, which makes it finer, stronger and smoother than carded or open end cotton. Combed ringspun also has the shortest fibres removed first, which is why it feels softer and pills less.