What Is GSM in Fabric?

GSM means grams per square metre (g/m²). It tells you how much one square metre of fabric weighs, which makes it the standard way to specify fabric weight for knitted, woven and nonwoven textiles. Because it is measured per unit area, GSM lets buyers and mills compare fabrics of different widths and roll lengths on the same basis.

How to Calculate Fabric GSM

You need two numbers: the sample weight in grams and the sample area. Convert the area to square metres and divide. This Fabric GSM Calculator converts every unit (mg, g, kg, oz, lb; mm, cm, m, inch, ft, yard) to grams and square metres before calculating, so mixed units give the same answer.

GSM Formula

GSM = sample weight (g) ÷ sample area (m²) GSM = weight (g) ÷ area (cm²) × 10,000 Circle: area = π × diameter² ÷ 4 100 cm² cutter: GSM = weight (g) × 100

Example: a 20 × 20 cm sample has an area of 400 cm² (0.04 m²). If it weighs 9.6 g, the fabric is 9.6 ÷ 0.04 = 240 GSM.

How to Measure GSM Using a Fabric Sample

1. Let the fabric relax and, for formal testing, condition it in the atmosphere your test method requires (commonly 20 °C and 65% relative humidity), because moisture changes weight.
2. Cut the sample cleanly with a GSM cutter or template, away from the selvage and any creases. Measure the real cut size.
3. Weigh it on a balance that reads to at least 0.01 g; 0.001 g is better for small samples.
4. Repeat across the width (left, centre, right) or along the roll (start, middle, end) and average the results.

Fabric mass per unit area is commonly tested with methods such as ASTM D3776 and ISO 3801. This calculator does the arithmetic only; it is not a certified laboratory. For formal testing and buyer acceptance, follow the applicable test method and specification required for your product.

What Is oz/yd²?

oz/yd² (ounces per square yard) is the imperial area weight used widely for denim, canvas and fleece in the US market. Like GSM it is independent of width: a 12 oz/yd² denim weighs 12 ounces for every square yard.

GSM to oz/yd² Conversion

oz/yd² = GSM ÷ 33.905747 GSM = oz/yd² × 33.905747

The factor comes from 1 oz = 28.349523 g and 1 yd² = 0.836127 m². So 200 GSM is about 5.90 oz/yd², and 12 oz/yd² is about 406.87 GSM. The calculator uses the full factor internally, not a rounded 34.

GSM vs Ounces per Linear Yard

“Ounces” on a fabric quote can mean two different things. oz/yd² is an area weight. Ounces per linear yard is the weight of one running yard at the full fabric width. A 60-inch-wide fabric at 6 oz/yd² weighs about 10 oz per linear yard, because the linear figure includes the width. Mixing the two is one of the most common sourcing mistakes, so always confirm which one is meant.

How Fabric Width Affects Linear Weight

grams per linear metre = GSM × width (m)

Width never changes GSM, but it changes how much each running metre weighs. A 200 GSM fabric weighs 300 g/m at 1.5 m wide and 360 g/m at 1.8 m wide. That matters when fabric is priced per kilo but consumed per metre.

How to Calculate Fabric Roll Weight

roll weight (g) = GSM × width (m) × length (m) roll length (m) = net weight (g) ÷ (GSM × width (m))

A roll of 200 GSM fabric, 1.5 m wide and 100 m long, has 150 m² of fabric and weighs 30 kg net. Working backwards, a 60 kg roll of the same fabric holds about 200 m. Real rolls differ because of actual width, moisture, selvage, finishing and winding tension, and cores and packing add to gross weight.

How to Calculate GSM from Multiple Samples

One sample tells you little about a roll. Test several and look at the spread:

mean = Σx ÷ n range = max − min sample SD = √(Σ(x − mean)² ÷ (n − 1)) population SD = √(Σ(x − mean)² ÷ n) CV% = SD ÷ mean × 100

For samples of 198, 202, 201, 199 and 200 GSM the mean is 200 GSM, the range 4 GSM, the sample standard deviation 1.58 GSM and the CV 0.79%. The calculator states which standard deviation it used so results are not silently mixed.

How to Check GSM Tolerance

± %: lower = target × (1 − tol%), upper = target × (1 + tol%) ± GSM: lower = target − tol, upper = target + tol

A 200 GSM target with ±5% gives an acceptable range of 190–210 GSM. There is no universal tolerance; it comes from your buyer or internal specification. A reading outside the range is a reason to investigate, not automatic proof of a defect.

Does Higher GSM Mean Better Fabric?

No. GSM is mass per area. It is not a direct measure of thickness, warmth, strength, quality, stretch or hand feel. Fabric performance also depends on fibre, yarn, knit or woven structure, density, finishing, coating, stretch, moisture and intended use. A lightweight performance knit can be the better choice for a running top than a heavier cotton jersey.

GSM for Knitted vs Woven Fabric

The measurement is the same for both: mass ÷ area. Knits are usually specified in GSM, while woven fabrics are often also described by construction (ends and picks per inch and yarn count). The Advanced mode estimates a theoretical woven GSM from EPI, PPI, yarn count and crimp, and a single-jersey knit GSM from course and wale density, loop length and yarn count. These are estimates; measured GSM decides.

Weight bands such as light (under about 150 GSM), medium (about 150–250 GSM) and heavy (about 250–350 GSM) are approximate industry-oriented categories, not universal standards.

Fabric GSM for Sportswear

Typical starting ranges: team jerseys about 130–180 GSM, performance tops about 120–180 GSM, polos about 180–240 GSM, leggings about 180–280 GSM, joggers about 240–340 GSM and hoodies about 280–400 GSM. Opacity, stretch recovery, breathability and the print method (for example sublimation on polyester) often matter more than the exact GSM. THIZ International manufactures custom sportswear and teamwear and can match fabric weight to your product and market.

Frequently Asked Questions