What Is GSM in Fabric? A Complete Weight Guide

Fabric weight is one of the first specifications a product developer locks down. Get it wrong and you end up with a t-shirt that's either see-through or stiff enough to stand on its own. GSM is the number that defines that weight — and understanding it is foundational to sourcing the right fabric for any application.

GSM Definition

GSM stands for grams per square meter. It is the universal measurement of fabric weight and density, used by mills, brands, and sourcing teams worldwide regardless of what unit system a country uses for everyday measurement.

The measurement is straightforward: cut a fabric swatch exactly 1 meter × 1 meter, weigh it on a precision scale, and the result in grams is the GSM. In practice, labs use a circular die cutter to punch out a standardized smaller swatch — typically 100 cm² — and multiply the result to arrive at the per-square-meter figure. The governing standard in the United States is ASTM D3776, which defines the test method for mass per unit area of woven and knit fabrics.

GSM reflects not just the raw material going into the fabric but the construction itself. A tighter loop, a denser stitch, or a heavier yarn all push GSM upward. Finishing operations — napping, shearing, compacting — also shift the finished GSM relative to the greige weight off the machine.

Why GSM Matters

GSM drives nearly every functional and commercial property of a knit fabric:

Hand feel and drape. Lower GSM fabrics are lighter and tend to drape fluidly. Higher GSM fabrics have more body and structure. A 140 GSM jersey flows; a 280 GSM jersey holds its shape.

Opacity. Thin, low-GSM fabrics transmit more light. For garments where coverage matters — workwear, activewear worn over compression layers — GSM directly affects whether you need a liner or a heavier base fabric.

Durability. More material per square meter means more fiber to resist abrasion, pilling, and repeated laundering. Industrial and workwear applications routinely specify higher GSM floors for this reason.

Warmth. Heavier fabrics trap more air and insulate better. Fleece and French terry are not warm by coincidence — they're engineered at high GSM to create thermal performance.

Cost. Fabric is priced by the yard or kilogram. Higher GSM means more yarn per yard, which means higher material cost. Specifying the minimum GSM that meets performance requirements is standard practice in cost-conscious development.

GSM Ranges by Fabric Type

The following ranges reflect what Beverly Knits produces on circular knitting machines across its product line.

Fabric Type | GSM Range | Weight Category

|---|---|---|

Mesh | 80–200 | Lightweight

Jersey | 120–280 | Light to Mid

Pique | 150–250 | Mid

Interlock | 180–320 | Mid to Heavy

Rib | 180–350 | Mid to Heavy

French Terry | 220–380 | Heavy

Fleece | 200–400 | Heavy

Double Knit | 250–450 | Heavyweight

These are production ranges, not theoretical limits. The actual achievable GSM for a given construction depends on yarn count, machine gauge, and stitch length. A 28-gauge machine running fine-count yarn will produce a different GSM ceiling than a 12-gauge machine running bulky yarn in the same fabric structure.

GSM by Application

Beyond fabric construction, end-use application drives GSM selection. These are typical specification ranges by product category:

Application | Target GSM Range

|---|---|

Athletic base layer | 110–150

T-shirts | 150–200

Polo shirts | 180–240

Sweatshirts | 280–340

Workwear | 200–300

Automotive textiles | 150–320

Mattress ticking | 180–280

Athletic base layers sit at the low end because breathability and moisture transport matter more than bulk. Sweatshirts cluster in the 280–340 range because consumers associate weight with quality and warmth. Automotive and mattress ticking span a wide range because the performance requirements vary significantly by specific application — a seat bolster fabric has different demands than a headliner or a mattress border.

GSM vs Oz/yd² Conversion

The US apparel industry still frequently quotes fabric weight in ounces per square yard (oz/yd²). Both units measure the same thing, and converting between them is a single calculation:

oz/yd² = GSM × 0.02949

Conversely: GSM = oz/yd² × 33.906

Quick reference:

GSM | oz/yd²

|---|---|

100 | 2.95

140 | 4.13

180 | 5.31

200 | 5.90

240 | 7.08

280 | 8.26

320 | 9.44

360 | 10.62

400 | 11.80

450 | 13.27

When a domestic supplier quotes 5.5 oz/yd² and an offshore quote comes in at 190 GSM, you are looking at essentially the same weight (5.5 oz/yd² = 187 GSM). The conversion eliminates unit confusion before it becomes a production problem.

How to Specify GSM When Ordering

Stating a GSM target in an inquiry or purchase order is not enough on its own. Precision in specifications prevents disputes and sampling iterations.

Specify a tolerance. A target GSM with no tolerance band is ambiguous. Standard practice is ±5% of the target weight. A 200 GSM spec with ±5% tolerance accepts fabric testing between 190 and 210 GSM.

Clarify greige versus finished weight. Fabric comes off the knitting machine at greige weight. After dyeing, finishing, and compacting, the weight shifts — typically 5–15% depending on the finishing process. If your spec is for finished fabric, state it explicitly. If the mill quotes greige weight, account for the difference.

Account for finishing shrinkage. Width and length can both change during finishing, which affects the areal density calculation. A fabric that compacts significantly will gain GSM even without added material. If dimensional stability is critical to your end product, specify post-wash GSM alongside as-finished GSM.

Request a test report. Any serious supplier should be able to provide ASTM D3776 test results from an accredited lab. Mill-reported GSM and certified test results are not always identical. For high-volume programs, independent testing before bulk production approval is standard practice.

Request Fabric Samples

Beverly Knits has manufactured circular knit fabrics in Gastonia, NC for over 40 years. The operation spans the full GSM range — from lightweight mesh at 80 GSM to heavyweight double knit above 400 GSM — across jersey, interlock, rib, pique, French terry, fleece, and specialty constructions.

If you are developing a product and need to evaluate fabric weight, hand, and performance before committing to a specification, contact Beverly Knits to request samples. Specify the fabric type, target GSM, fiber content, and end use, and the team will work with you to identify constructions that match your requirements.