To convert ounces per square yard to GSM, we multiply the fabric weight by 33.90575. To convert GSM back to ounces per square yard, we divide by 33.90575. The formula applies to area weight in oz/yd². If a source gives ounces per linear yard, we also need the fabric width.
Enter a nonnegative value in either converter. We keep the NIST-based factor through the calculation and display the result to two decimal places.
Conversion factor: 1 oz/yd² = 33.90575 GSM.
We use the conversion factor published in NIST SP 811 Appendix B.8. NIST lists one ounce per square yard as 0.03390575 kilograms per square meter. Multiplying kilograms by 1,000 produces 33.90575 grams per square meter.
GSM = oz/yd² × 33.90575
oz/yd² = GSM ÷ 33.90575
For a quick estimate, multiplying by 34 is close. The shortcut factor is about 0.278% higher than 33.90575, so we use the full factor when a specification or purchasing comparison needs consistent rounding.
We calculated each table value with 33.90575 and rounded the displayed result to two decimal places.
| oz/yd² | GSM | Calculation |
|---|---|---|
| 1 | 33.91 | 1 × 33.90575 |
| 2 | 67.81 | 2 × 33.90575 |
| 3 | 101.72 | 3 × 33.90575 |
| 4 | 135.62 | 4 × 33.90575 |
| 5 | 169.53 | 5 × 33.90575 |
| 6 | 203.43 | 6 × 33.90575 |
| 7 | 237.34 | 7 × 33.90575 |
| 8 | 271.25 | 8 × 33.90575 |
| 9 | 305.15 | 9 × 33.90575 |
| 10 | 339.06 | 10 × 33.90575 |
| 12 | 406.87 | 12 × 33.90575 |
| 14 | 474.68 | 14 × 33.90575 |
| 16 | 542.49 | 16 × 33.90575 |
| 18 | 610.30 | 18 × 33.90575 |
| 20 | 678.12 | 20 × 33.90575 |
| 24 | 813.74 | 24 × 33.90575 |
| 30 | 1,017.17 | 30 × 33.90575 |
A mass stated per linear yard cannot be converted to GSM until we know the fabric width. If a fabric weighs M ounces per linear yard and has a finished width of W inches, we first calculate ounces per square yard, then calculate GSM.
oz/yd² = 36M ÷ W
GSM = (36M ÷ W) × 33.90575
For example, a hypothetical fabric that weighs 8 ounces per linear yard at 60 inches wide has an area weight of 4.8 oz/yd². The converted result is 162.75 GSM. A different width changes the result even when the ounces per linear yard stay the same.
A catalog example shows the same distinction. Our 22 oz-per-linear-yard velour material in 61-inch width is also listed at 13 oz/yd². The width-aware formula gives 12.98 oz/yd² before rounding, consistent with the listed 13 oz/yd²; 13 oz/yd² converts to 440.77 GSM.
At Canvas ETC, we treat converted weight as one field in a specification. We also identify material, width, weave, finish or coating, and intended end use. Those fields separate fabrics that carry the same nominal area weight but use different fibers or constructions. Material Cotton, linen, polyester, nylon, or a blended construction. Weight or denier Use oz/yd² or GSM for area weight. Use denier for yarn linear density. Width Record the usable or finished width that applies to the purchase. Weave State the fabric construction, including duck or ripstop where relevant. Finish or coating Name wax, vinyl, priming, water-repellent treatment, or another supplied finish. End use Match the specification to bags, covers, artist canvas, marine work, awnings, apparel, or another defined application.
Our catalog examples show how the same unit conversion sits beside other specifications. The 10.10 oz Army Duck canvas in 37-inch width converts to 342.45 GSM, while the 10 oz unprimed linen art canvas in 88-inch width converts to 339.06 GSM. The linked titles identify different fabric categories and widths. The 18 oz black vinyl polyester in 61-inch width converts to 610.30 GSM, and the 24 oz #4 dyed cotton fabric in 60-inch width converts to 813.74 GSM.
These calculations translate the area weights stated on the linked product pages. They do not state current availability or replace a current product specification or lot test. We check the product page before a production decision.
GSM states nominal mass per square meter. Equal GSM values do not establish equal thickness, yarn size, weave, coating, hand, or tested performance. We keep those attributes separate when we compare textiles.
| Attribute | What it describes | How we use it |
|---|---|---|
| GSM or oz/yd² | Mass per unit area | Convert between unit systems and compare nominal area weight. |
| Thickness | Distance between fabric surfaces under a defined method | Use a separate thickness value when the application depends on bulk or clearance. |
| Denier | Yarn mass per unit length | Use construction data rather than a direct GSM conversion. Our guide to choosing fabric by denier covers that selection path. |
| Numbered duck | A traditional cotton duck classification | Use the numbered duck system instead of treating the number as GSM. |
| Width and yardage | Usable span and purchase length | Use weight with width and the project plan. Our fabric yardage calculations address quantity rather than area-weight conversion. |
For deeper material context, we maintain separate references for duck canvas weights and linen fabric weights and GSM.
One ounce per square yard equals 33.90575 grams per square meter. Rounded to two decimal places, 1 oz/yd² is 33.91 GSM.
We divide 300 by 33.90575. The result is 8.85 oz/yd² when rounded to two decimal places.
We multiply 7 by 33.90575. The result is 237.34 GSM when rounded to two decimal places.
We multiply 8 by 33.90575. The result is 271.25 GSM when rounded to two decimal places.
We use the converted number to narrow a specification, then check material, width, weave, finish or coating, and end use before a production decision.
