Jiashun / Fabric tools / 01
Fabric GSM calculator& GSM to oz/yd² converter
Measure a swatch. Convert a fabric spec. Find a starting weight for your next garment. Free to use, with no signup.
Quick reference
400 GSM ≈ 11.8 oz/yd²
Enter a fabric weight to convert it, or measure a rectangular swatch to estimate GSM. Your calculation will appear here.
A conversion changes the unit, not the cloth. GSM does not directly measure thickness, warmth or quality.
Fabric finder / For your next sample
Which fabric weight fits your brief?
Choose your product, feel and wearing context. Get a starting GSM range and a fabric direction to discuss with our team.
A number is the starting point
Choose the cloth.
Then confirm the garment.
Your result includes a candidate weight range, a fabric construction to explore and what to compare in a physical sample.
GSM measures mass per area. It cannot tell you softness, warmth or quality on its own.
Already have a swatch or an ounce weight? Use the fabric GSM calculator →
The calculation
How to calculate fabric GSM
GSM means grams per square metre: fabric mass divided by fabric area. Measure the length and width of one rectangular swatch, weigh it, and convert the area to square metres.
GSM = weight (g) ÷ area (m²)
Example: a 10 × 10 cm swatch
A 10 × 10 cm swatch covers 0.01 m². If it weighs 2.4 g, its estimated GSM is 2.4 ÷ 0.01 = 240 GSM. For centimetre inputs, GSM = weight (g) × 10,000 ÷ (length × width).
Make the measurements comparable
Use an accurate scale, measure the specimen carefully and compare the same finished fabric state. A small cutting gives a practical estimate, not a laboratory test report or proof that an entire roll is consistent.
Metric ↔ Imperial
GSM to oz/yd² chart
Divide GSM by approximately 33.906 to get ounces per square yard. Multiply oz/yd² by the same factor to convert back.
| GSM / g/m² | oz/yd² |
|---|---|
| 180 | 5.31 |
| 220 | 6.49 |
| 240 | 7.08 |
| 280 | 8.26 |
| 320 | 9.44 |
| 400 | 11.80 |
| 450 | 13.27 |
| 500 | 14.75 |
Before you choose the cloth
Does higher GSM mean better quality?
No. GSM reports mass per area. Composition, yarn, construction and finishing can make two fabrics with the same GSM behave differently. Use our streetwear fabric weight guide to compare candidates and plan sampling.
Does a 400 GSM hoodie weigh 400 grams?
No. The finished garment includes differently sized panels, rib, pockets, trims and sometimes multiple layers. Fabric weight is not finished garment weight or shipping weight.
Are oz/yd² and ounces per yard the same?
No. oz/yd² is mass per square yard. Weight per running yard also depends on fabric width. This converter uses area weight only; confirm which unit your supplier means by “oz”.
Can Jiashun help source the fabric?
Share your product, target feel, composition and weight direction. Our fabric sourcing process connects that brief to candidate swatches and sample approval.