Converters · fabric
GSM to oz/yd² fabric weight converter.
Convert g/m² (gsm) to ounces per square yard and per square foot, and back, with exact factors. Check where a fabric sits on the sheer-to-heavy scale, load a denim or canvas weight, or find what a piece of cloth weighs. Runs in your browser; nothing is sent or stored.
Fabric weight
Result
Worked example
A fabric listed as 200 gsm weighs 200 g per square metre. A square yard is 0.9144 m x 0.9144 m = 0.83612736 m², so it weighs 200 x 0.83612736 = 167.2 g, which is 167.2 / 28.349523125 = 5.90 oz/yd². Going the other way, a 12 oz denim is 12 x 33.9057 = 406.9 gsm.
Formula and sources
Method: 1 oz/yd² = 28.349523125 g / (0.9144 m)² = 33.9057 g/m²; 1 oz/ft² = 28.349523125 g / (0.3048 m)² = 305.1517 g/m². Both are exact because the avoirdupois ounce (1/16 of 0.45359237 kg), the international yard (0.9144 m) and the foot (0.3048 m) are defined, not measured. gsm to oz/yd²: divide by 33.9057. oz/yd² to gsm: multiply by 33.9057. Piece weight = length x width in metres x gsm.
Source for the factors: NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B.8 conversion factors: oz/yd² to kg/m² is 3.390 575 E-02 and oz/ft² to kg/m² is 3.051 517 E-01, which match the figures above (page read 2026-10-02). The ounce, yard and foot definitions are also in NIST Handbook 44, Appendix C.
Measuring fabric weight: mass per unit area of a woven fabric is tested to ISO 3801 (textiles, woven fabrics, mass per unit length and mass per unit area) and ASTM D3776 (standard test methods for mass per unit area of fabric). Test results depend on conditioning, so a mill's quoted weight can differ a little from a home measurement.
Classes are trade convention: the bands below are our rule of thumb from common trade usage. They are not defined by NIST, ISO or ASTM, and sellers draw the lines differently. General fabric: sheer under 100 gsm, light 100 to 149, medium 150 to 249, heavy 250 to 399, very heavy 400 and up. Denim: under 10 oz/yd² lightweight, 10 to 14 midweight, over 14 heavyweight.
Denim oz to gsm
| Denim weight | Grams per m² | Class (convention) |
|---|---|---|
| 10 oz/yd² | 339.1 gsm | Midweight denim |
| 11 oz/yd² | 373.0 gsm | Midweight denim |
| 12 oz/yd² | 406.9 gsm | Midweight denim |
| 13 oz/yd² | 440.8 gsm | Midweight denim |
| 14 oz/yd² | 474.7 gsm | Midweight denim |
Canvas oz to gsm
| Canvas weight | Grams per m² | Per square foot |
|---|---|---|
| 8 oz/yd² | 271.2 gsm | 0.889 oz/ft² |
| 10 oz/yd² | 339.1 gsm | 1.111 oz/ft² |
| 12 oz/yd² | 406.9 gsm | 1.333 oz/ft² |
| 15 oz/yd² | 508.6 gsm | 1.667 oz/ft² |
| 18 oz/yd² | 610.3 gsm | 2.000 oz/ft² |
GSM to oz/yd² quick table
| gsm | oz/yd² | oz/ft² | Class (convention) |
|---|---|---|---|
| 100 gsm | 2.95 oz/yd² | 0.328 oz/ft² | Light |
| 120 gsm | 3.54 oz/yd² | 0.393 oz/ft² | Light |
| 150 gsm | 4.42 oz/yd² | 0.492 oz/ft² | Medium |
| 180 gsm | 5.31 oz/yd² | 0.590 oz/ft² | Medium |
| 200 gsm | 5.90 oz/yd² | 0.655 oz/ft² | Medium |
| 250 gsm | 7.37 oz/yd² | 0.819 oz/ft² | Heavy |
| 300 gsm | 8.85 oz/yd² | 0.983 oz/ft² | Heavy |
| 400 gsm | 11.80 oz/yd² | 1.311 oz/ft² | Very heavy |
Boundary: this converts and describes a weight per area. It does not know fibre, weave, drape or quality: two fabrics of the same gsm can feel very different, and a garment's weight is not its fabric's gsm.
Frequently asked questions
How do I convert gsm to oz/yd²?
Divide grams per square metre by 33.9057 (or multiply by 0.029494). 200 gsm / 33.9057 = 5.90 oz/yd². The factor is exact: one avoirdupois ounce is 28.349523125 g and one international yard is 0.9144 m, so one square yard is 0.83612736 m².
How many gsm is a 12 oz denim?
12 oz/yd² x 33.9057 = 406.9 gsm. A 10 oz denim is 339.1 gsm and a 14 oz denim is 474.7 gsm. Denim is sold by the ounce weight of a square yard of cloth, not of a finished garment.
How many gsm is 10 oz canvas?
10 oz/yd² is 339.1 gsm. Canvas is usually sold by that oz/yd² weight, but "duck number" grades differ between mills and are not defined by one public standard, so check the oz/yd² figure on the spec sheet rather than converting a duck number.
Is oz/yd² the same as oz/ft² or fluid ounces?
No. A square yard is 9 square feet, so oz/ft² is one ninth of oz/yd² (1 oz/yd² = 0.1111 oz/ft² = 33.9057 gsm; 1 oz/ft² = 305.1517 gsm). These are ounces of mass (avoirdupois), not fluid ounces.
What gsm is a T-shirt?
Most adult T-shirts are roughly 150 to 200 gsm (about 4.4 to 5.9 oz/yd²). Under about 150 is a light summer tee and above about 200 a heavyweight tee. That range is a trade convention, not a standard, and it is the weight of the fabric, not of the shirt.
How do I find the weight of a piece of fabric?
Multiply length by width to get the area in square metres, then multiply by gsm. A piece 2 m long and 1.5 m wide at 180 gsm is 3 m² x 180 = 540 g (19.05 oz). Use the piece weight section above to enter any length and width.