What Is GSM in Fabric?

GSM stands for Grams per Square Meter. It is the international standard measure of fabric weight in apparel manufacturing. A 220 GSM cotton jersey weighs 220 grams per square meter of fabric.

GSM tells you two things at once: how heavy the fabric feels in hand, and how much it costs per meter. Both directly map to whether the garment fits the brand's positioning and unit-economics target.

Why GSM matters

Fabric weight is the single biggest variable in apparel feel. A 140 GSM jersey is a thin, breathable summer tee. A 320 GSM jersey is a heavyweight hoodie body fabric. A 480 GSM French terry is a premium streetwear sweatshirt fabric. Same fiber, same family, vastly different garments.

Fabric weight also drives cost. Heavier fabric uses more yarn per garment. A 320 GSM hoodie body costs roughly twice as much in fabric as a 140 GSM tee body. Brand pricing has to account for the fabric-weight delta the brand chose.

Typical GSM ranges by garment

1. Lightweight summer tee: 140 to 170 GSM cotton jersey.
2. Standard everyday tee: 180 to 220 GSM cotton or cotton-blend jersey.
3. Heavyweight premium tee: 230 to 280 GSM jersey (typically combed-ring-spun cotton).
4. Athletic tee or activewear top: 130 to 180 GSM polyester or poly-spandex.
5. Hoodie body (knit): 280 to 380 GSM French terry or fleece, lined or unlined.
6. Premium streetwear hoodie: 400 to 500 GSM heavyweight fleece.
7. Leggings and activewear bottoms: 200 to 320 GSM (depending on opacity requirement; below 220 GSM is typically not "squat-proof").
8. Swimwear (warp-knit nylon-spandex): 180 to 230 GSM.
9. Bralette / soft intimates: 80 to 140 GSM (jersey, modal, or microfiber).
10. Outerwear shell fabric (wovens): 100 to 240 GSM depending on category.

How to spec GSM in a tech pack

GSM appears on the Bill of Materials page of the tech pack. Standard format is the GSM number, the fiber composition, and the construction type. For example: `220 GSM, 95% Cotton 5% Spandex, single jersey`.

Acceptable tolerance is plus or minus 5 percent of stated GSM. Factories should hit this on a calibrated fabric scale. Out-of-tolerance lots get rejected at fabric inspection.

GSM versus oz/sq yd

In the US, fabric weight is sometimes specified in ounces per square yard (oz/yd2). Conversion: 1 oz/yd2 equals approximately 33.9 GSM. A 7 oz/yd2 cotton jersey is approximately 237 GSM. International factories work in GSM. Always cross-check the unit when sharing specs across US and Asian counterparties.

GSM and squat-proof leggings

A specific commercial question: at what GSM do leggings become opaque under stretch? For most polyester-spandex blends, 240 GSM is the floor for squat-proof opacity. Below that, the fabric goes sheer at stretch. Lululemon's signature Luon hits 245 to 260 GSM. Knock-off versions often drop to 200 GSM, which is why they go sheer.

Related terms

• What is a tech pack covers the document where GSM is specified.
• What is OEKO-TEX certification addresses the chemical safety side of fabric spec.
• Cotton vs polyester for apparel explores the fiber-choice tradeoff that interacts with GSM.