Three numbers and two words on a label tell you almost everything about how a t-shirt will behave: the GSM, the fiber percentages, and the knit name. This t-shirt fabric guide explains what each one means in practice, so you can predict drape, durability and shrinkage before you ever try the shirt on.
The short version: GSM tells you weight and opacity, the fiber blend tells you comfort and shape retention, and the knit structure tells you texture and stretch. Everything else is finishing.
What GSM means and why it decides the drape
GSM stands for grams per square meter. It is the weight of the fabric, not the thickness of the yarn, and it is the single most useful number on a tee label.
Lower GSM fabric is lighter, more breathable, more likely to be semi-sheer, and it drapes closer to the body because there is less mass to hold a shape. Higher GSM fabric is opaque, holds its own structure, hangs away from the body, and takes a hem or a shoulder seam more cleanly.
A rough map of the ranges you will actually encounter:
| GSM range | Weight class | How it behaves |
|---|---|---|
| 110 to 140 | Very light | Soft, fluid, often semi-sheer. Good for hot weather and layering under things |
| 150 to 180 | Light to mid | The common everyday tee weight. Breathable, drapes softly, moderate opacity |
| 180 to 220 | Mid to heavy | Opaque, holds a shoulder line, stands slightly away from the body |
| 220 to 280 | Heavy | Structured, boxy, very durable, slow to dry, warm |
| 280 and up | Very heavy | Closer to a lightweight sweatshirt than a tee |
If you like a tee that skims and moves, look at 150 to 180. If you want one that keeps its shape over a long day and does not cling, look at 190 to 230. The complaint "this tee has no structure" is almost always a GSM problem, not a sizing one.
One caveat: GSM is not a quality score. A badly spun 220 GSM fabric will pill faster than a well-made 160. Weight tells you behavior. Fiber quality tells you longevity.
Cotton types, in plain terms
Not all cotton on a label is the same cotton.
Carded cotton has been mechanically cleaned and aligned, with short fibers still present. It is the standard, it is cheaper, and it has a slightly rougher hand and a greater tendency to pill, because short fiber ends work their way to the surface.
Combed cotton has gone through an extra step that removes the short fibers and impurities. The result is a smoother surface, a stronger yarn and noticeably less pilling over time. On a label it is worth paying for.
Ring-spun describes how the yarn was twisted rather than how it was cleaned. Ring-spun yarn is continuously twisted and thinner for its strength, which gives a softer, finer feel than open-end spinning. "Combed ring-spun cotton" is the phrase that signals a well-made cotton tee.
Long-staple cotton refers to fiber length. Longer fibers mean fewer ends per inch of yarn, which means smoother fabric and less pilling. Terms like Pima and Egyptian cotton refer to long-staple varieties.
Organic describes how the crop was grown, not how the fabric performs. A well-made conventional combed tee will outlast a poorly made organic one.
This t-shirt fabric guide to blends: what each fiber adds
Blends exist to patch the weaknesses of pure cotton, which are shrinkage, wrinkling and slow drying.
100% cotton. Breathable, absorbent, soft, takes dye well. Shrinks, wrinkles, dries slowly, and loses shape at stress points over time.
Cotton and polyester. Polyester adds dimensional stability, wrinkle resistance and faster drying, and it dramatically reduces shrinkage. It also reduces breathability and can hold odor more readily. A 60/40 or 50/50 blend is a genuine middle ground; anything above about 65% polyester starts to feel noticeably synthetic.
Tri-blend. Cotton, polyester and rayon or viscose together. The rayon adds a fluid, slinky drape and a faded, heathered look. Tri-blends feel exceptional and are the least structured option available, so they are a poor choice if you want a crisp shoulder.
Cotton and elastane. Usually 95/5. Adds stretch and a close fit that recovers, which is why it is common in fitted tees. Elastane is the fiber most easily destroyed by heat, so this blend is the one that most needs a cool wash and no dryer.
Cotton and modal or lyocell. Adds a smooth, cool hand and good drape with better shape retention than rayon. Softer than cotton, more expensive, and slightly more delicate in the wash.
100% polyester. Fast drying, shape stable, very durable. It belongs in training kit rather than in an everyday tee, where it can feel slick at rest and holds odor more readily than cotton.
Knit structures and the texture they create
The knit is how the yarn is looped together. Same fiber, same GSM, completely different shirt.
Single jersey. The default tee knit. Smooth face, looped back, stretches more across the body than down its length. Light, breathable, and prone to curling at raw edges.
Interlock. Two jersey layers knitted together, so both faces are smooth. Denser, more stable, less prone to curling, better opacity at the same weight. It feels more substantial and costs more.
Slub. Jersey knitted from deliberately uneven yarn, giving a subtly irregular, textured surface. Visually warmer than flat jersey and very good at hiding creases.
Pique. A textured, slightly waffled knit, most familiar from polo shirts. Breathable, holds structure, resists showing wrinkles.
Ribbed. Alternating raised and recessed columns. High stretch across the body with strong recovery, which is why it is used for collars and cuffs as well as whole garments.
Waffle and thermal. A raised grid structure that traps air. Warmer than its weight suggests, with a lot of texture.
How fabric choice decides shrinkage
Shrinkage is mostly a cotton issue, and it is mostly preventable.
Cotton fibers are stretched under tension during spinning and knitting. Heat and agitation let them relax back, and the fabric contracts. That is why almost all shrinkage happens in the first wash and the first tumble dry.
What reduces it:
- Pre-shrunk or compacted fabric. The mill has already relaxed the fabric before cutting. Labels may say pre-shrunk or compacted.
- Polyester in the blend. Polyester does not relax the way cotton does, so it holds the fabric’s dimensions.
- Cool water and low or no heat in drying. Heat is the main trigger. Air drying a 100% cotton tee removes most of the risk.
Expect a 100% cotton tee that is not pre-shrunk to lose a little length on first wash, and more if it goes through a hot dryer. Length goes before width on a jersey knit, which is why tees come up short rather than tight.
T-shirt fabric guide checklist: reading the label
Before you buy, read for these six things in order.
- GSM, for drape and opacity. If it is not listed, the garment weight in grams plus the size is a usable proxy.
- Fiber percentages, for comfort, stretch and shape retention.
- Combed, ring-spun or long-staple, for how it will look after thirty washes.
- Knit name, for texture and edge stability.
- Pre-shrunk or compacted, for how much it will move in the first wash.
- Care instructions, because elastane, modal and rayon content all narrow what you can do with heat.
Buying from the label
Once you can read those six things, you stop guessing. A 180 GSM combed ring-spun single jersey will be a soft, draping everyday tee that needs a careful first wash. A 210 GSM interlock in a cotton-polyester blend will hold its shoulder line, resist wrinkles and barely move in the wash. Neither is better. They are different tools.
Check the fabric details on each tee listed on the Shop page and match the weight and blend to how you actually want the shirt to sit.