What is Fabric Weight (GSM)?

Fabric weight is the mass of one square meter of fabric in grams (g/m²). It is known as GSM (grams per square meter): a fabric of 150 g/m² weighs 150 g per square meter. GSM shows whether a fabric is light or heavy, but it is not a measure of thickness or quality. Turkish suppliers call it gramaj.

How is fabric weight measured?

Mass per unit area is measured to a standard; which standard applies depends on the fabric type.

For a quick check, cut a 10 × 10 cm (100 cm²) piece of fabric, weigh it and multiply the result by 100. A specimen of 160 g/m² fabric weighs only 1.6 g, so use a balance accurate to at least 0.01 g. In its laboratory practice, Dönmez (2008) used a 10 × 10 cm template, a balance accurate to 1 mg, fabric rested flat for 48 hours, and 10 specimens from different points.

What GSM tells you, and what it does not

• It is not thickness. Thickness is a separate measurement (ISO 5084).
• It does not describe structure. The same GSM can be reached with a fine yarn knitted tightly or a coarse yarn knitted loosely (Cotton Incorporated, ISP 1009). In knitting, weight falls as the loop yarn length increases (Dönmez, 2008).
• It is not a synonym for quality. Printful writes that quality comes from matching fabric weight to the intended use, not from chasing the highest GSM.

Greige, finished, relaxed: the state of measurement

The weight of a knitted fabric changes with the state in which it is measured: as the fabric relaxes, the loops draw closer together and the weight rises. According to ISP 1009, a single jersey knitted from Ne 30/1 combed ring-spun yarn on a 28-gauge machine weighed 135 g/m² as it came off the machine and 176 g/m² when fully relaxed (an increase of about 30%). The dyed and finished version of the same fabric measured 149 g/m² as delivered and 166 g/m² relaxed. So when you write a weight, also write the state in which it was measured.

Units and conversion

• oz/yd² (ounces): 1 oz/yd² is 0.03390575 kg/m², i.e. about 33.9 g/m² (NIST SP 811). Example: 5.3 oz/yd² is about 180 g/m².
• Denim: Weight is mostly given in oz/yd². According to Cotton Incorporated, finished denims range from 3.5 to 16.5 oz/yd²: 3.5–8 oz is used in blouses, tops and shirts, and 8–16.5 oz in trousers, jeans and jackets (CottonWorks). These ranges correspond to about 119–271 and 271–559 g/m² (calculation).
• Grams per running meter: ISO 3801 defines mass per unit length separately. If a fabric is quoted in grams per meter, g/m² = g/m ÷ open width (m). Example: at 1.5 m open width, 240 g per meter is 160 g/m². In a quote, ask which unit is used and whether the width is tubular or open.

Weight ranges

There is no standard limit for light, medium and heavy. For T-shirts, Printful gives roughly 120–150 g/m² as light, 150–180 as medium and 180–254 as heavy (May 7, 2026). For T-shirt single jersey, knitted-fabric manufacturers publish ranges of 120–180 g/m² (Karcem, September 2026) and 120–220 g/m² (RT Tekstil, June 2026). For detailed ranges by product, see the guide to GSM for T-shirts, hoodies and joggers.

How to write it in a quote

Write the weight not as a single figure but together with the structure, composition, yarn, target value, tolerance, state of measurement and standard. Example: “Single jersey, 100% cotton, Ne 30/1 combed, 160 g/m², ±5%, finished and relaxed, EN 12127”. A tolerance is not a standard but a contract clause.

For fabric sold by the kilogram, the meters per kilogram are 1,000 ÷ (GSM × open width in m). For 180 g/m² fabric at 1.80 m open width, 1 kg is about 3.09 m.

Frequently asked questions

Are GSM and gramaj the same?

Yes. Gramaj is the Turkish term; GSM is its English abbreviation (grams per square meter).

Does higher GSM mean better quality?

Not on its own. GSM tells you the weight of the fabric; yarn, structure, density and finishing also determine quality.