Fabric GSM Calculator (g/m² and oz/yd²)
What GSM means
GSM (grams per square meter) is the standard measure of fabric and paper weight. A heavier GSM means a denser or thicker material: a summer T-shirt might be 130–160 GSM, a hoodie 300+ GSM. Because it's a weight per area, you can measure it from a small sample: cut a precise area, weigh it, and scale up to one square meter.
How the calculation works
GSM = sample weight (g) × 10,000 ÷ sample area (cm²)
With the standard 100 cm² circle cutter, that simplifies to GSM = weight in grams × 100. To convert to ounces per square yard, divide by 33.906 (1 oz/yd² = 33.906 g/m²).
Worked example
A 100 cm² disc cut from a jersey knit weighs 1.85 g. GSM = 1.85 × 100 = 185 GSM, or 185 ÷ 33.906 = 5.46 oz/yd². If you cut through two layers at once, the 3.70 g reading is divided by 2.
Getting accurate GSM readings
- Use a scale that reads 0.01 g or better. Each 0.01 g on a 100 cm² sample is 1 GSM. A 0.1 g scale can't tell 180 from 190 GSM.
- Cut cleanly. A circular GSM cutter gives an exact, repeatable area; scissors and a ruler introduce area errors.
- Condition samples. Fabric absorbs moisture. Standard methods condition samples at controlled temperature and humidity before weighing; at minimum, don't weigh straight from a humid room or a hot dryer.
- Average several samples. Cut 3–5 discs across the width of the fabric and average them.
Our YP2002 textile scale with GSM cutter pairs a 2000 g × 0.01 g balance with a circular fabric sample cutter for exactly this test.
FAQ
Is GSM the same as fabric thickness?
No. GSM is mass per area; thickness depends on construction. A loose knit can be thick but light.
How do I convert oz/yd² to GSM?
Multiply by 33.906. 8 oz/yd² ≈ 271 GSM.
Does GSM apply to paper?
Yes. Paper weight is also given in g/m² (printer paper is commonly 75–90 GSM).
More tools: free lab calculators.
