Quick answer
How is GSM calculated?
GSM = weight of the sample in grams ÷ area of the sample in square metres. With a standard 100 cm² GSM cutter, multiply the disc weight by 100.
Sample area (m²) = Length (m) × Width (m)
How it works
GSM Calculator
Calculate fabric GSM from a cut swatch — enter its weight and size to get grams per square metre and ounces per square yard.
GSM is the weight of one square metre of fabric. Weigh a swatch of known size and scale the weight up to one square metre.
Formula
The formula, in full
- Sample area (m²)
- Length (m) × Width (m)
- GSM
- Sample weight (g) ÷ Sample area (m²)
- GSM cutter shortcut
- Weight of a 100 cm² disc × 100
- oz/yd²
- GSM × 0.029494
Example
10 × 10 cm swatch weighing 1.85 g
- 01Area = 0.1 × 0.1 = 0.01 m²
- 02GSM = 1.85 ÷ 0.01 = 185 g/m²
- 03= 5.46 oz/yd²
Use “Load Example” above to run this example in the calculator.
Industry tip
Industry tip
“Condition swatches for 24 hours at 65% RH and 20 °C before weighing — moisture can shift cotton GSM by several grams.”
Assumptions
What this calculator assumes
- The swatch is cut accurately to the size entered.
- Weight classes are a general industry guide, not a standard.
FAQ
Frequently asked questions
How is GSM calculated?
GSM = weight of the sample in grams ÷ area of the sample in square metres. With a standard 100 cm² GSM cutter, multiply the disc weight by 100.
What is a good GSM for T-shirts?
Basic T-shirts are typically 140–180 GSM single jersey; premium heavyweight tees are 200–260 GSM.
How do I convert GSM to oz?
oz/yd² = GSM × 0.0295. For example, 340 GSM denim ≈ 10 oz.