GSM to oz converter and fabric GSM calculator
Fabric weight as mass per unit area from a weighed sample of known size, in g/m² and oz/yd².
How this is calculated
GSM = sample weight (g) ÷ sample area (m²). Areas are converted with 1 m² = 10,000 cm² and 1 in² = 6.4516 cm²; weights with 1 oz = 28.3495 g. Ounces per square yard = GSM ÷ 33.906, since 1 oz/yd² = 28.3495 g ÷ 0.836127 m².
Worked example. A 100 cm² (0.01 m²) disc weighs 1.85 g. GSM = 1.85 ÷ 0.01 = 185 g/m², which is 185 ÷ 33.906 = 5.46 oz/yd².
GSM to oz/yd² conversion tables
Use these tables to read a weight in either unit without a calculator. Every value is computed from 1 oz/yd² = 33.906 g/m², the same factor the calculator uses.
| GSM (g/m²) | oz/yd² |
|---|---|
| 100 | 2.95 |
| 120 | 3.54 |
| 140 | 4.13 |
| 150 | 4.42 |
| 160 | 4.72 |
| 180 | 5.31 |
| 200 | 5.90 |
| 220 | 6.49 |
| 240 | 7.08 |
| 250 | 7.37 |
| 280 | 8.26 |
| 300 | 8.85 |
| 320 | 9.44 |
| 340 | 10.03 |
| 350 | 10.32 |
| 400 | 11.80 |
| 450 | 13.27 |
| 500 | 14.75 |
| oz/yd² | GSM (g/m²) |
|---|---|
| 3 | 102 |
| 4 | 136 |
| 5 | 170 |
| 6 | 203 |
| 7 | 237 |
| 8 | 271 |
| 9 | 305 |
| 10 | 339 |
| 11 | 373 |
| 12 | 407 |
| 13 | 441 |
| 14 | 475 |
| 16 | 542 |
Reading the result. In common trade usage fabrics below about 150 GSM are called light, those between about 150 and 250 GSM medium, and those above about 250 GSM heavy. These are habits, not standards, and the bands shift by fabric type: a 7 oz/yd² (about 237 GSM) denim is considered light for denim but heavy for a shirting.
Questions
- Why is the round cutter 100 cm²?
- Because 100 cm² is one hundredth of a square metre, the sample weight in grams multiplied by 100 is the GSM. A 1.85 g disc is a 185 GSM fabric.
- Does moisture matter?
- Yes. Cotton can change weight by several percent with humidity. Test standards condition samples in a standard atmosphere (20 °C, 65% RH) before weighing; results from an unconditioned sample on a humid floor will read heavy.
- How many samples should I cut?
- Take several specimens across the width, avoiding the selvedge, and average them. One disc tells you about one spot of the roll.
- How much is 14 oz fabric in GSM?
- If 14 oz means ounces per square yard, multiply 14 by 33.906. The result is about 475 GSM. A weight quoted per linear yard also needs the fabric width, so check the unit before using this conversion.
- What are 200 GSM, 240 GSM and 255 GSM in oz?
- Divide each weight in grams per square meter by 33.906. Rounded to two decimal places, 200 GSM is 5.90 oz/yd², 240 GSM is 7.08 oz/yd² and 255 GSM is 7.52 oz/yd². These are area weights, not the weight of a finished garment.
- What are 340 GSM and 400 GSM in oz?
- A 340 GSM fabric is about 10.03 oz/yd². A 400 GSM fabric is about 11.80 oz/yd². Use the same factor for both: GSM ÷ 33.906. Compare fabrics over the same area when judging which is heavier.
- Does a higher GSM mean better fabric?
- A higher GSM means more mass over the same area. It gives you a heavier fabric, but it does not prove better strength, comfort or quality. Yarn, fibre, weave or knit structure, and finish also affect how a fabric performs. Compare the result with the requirements of the intended garment.
- How do I convert GSM to ounces per square yard?
- Divide the GSM by 33.906. A 340 GSM fabric is 340 ÷ 33.906 = 10.03 oz/yd². To go the other way, multiply ounces per square yard by 33.906, so 12 oz/yd² is about 407 GSM.
- Is ounces per square yard the same as ounces per linear yard?
- No. Ounces per square yard (oz/yd²) is a weight per unit of area and does not depend on width. Ounces per linear yard depends on the fabric width, so the same cloth is a larger number on a wider roll. Check which one a specification means before converting.
- Why is denim sold in ounces and T-shirt fabric in GSM?
- It is trade habit. Denim mills have long quoted weight in ounces per square yard, while knit and shirting mills usually quote GSM. They measure the same thing, so use the table above to move between them.
- What is a typical GSM for a T-shirt?
- There is no standard. Single jersey T-shirt fabric is commonly in the range of roughly 140 to 200 GSM, with lighter fabrics feeling thin and heavier ones feeling more structured. The right figure depends on the buyer, the yarn and the fibre, so use the specification you were given.
Read the full guide
Sources & verification
Mass per unit area is defined in ASTM D3776/D3776M (Mass Per Unit Area (Weight) of Fabric) and ISO 3801 for woven fabrics. Unit factors are the exact international definitions of the ounce, yard and inch. The worked example is recomputed in the automated tests.