Fabric Weight Converter

Frequently Asked Questions

How do I convert GSM to oz/yd²?

Divide GSM by 33.906 to get ounces per square yard. A 200 GSM jersey is about 200 ÷ 33.906 ≈ 5.9 oz/yd².

How do I convert oz/yd² to GSM?

Multiply oz/yd² by 33.906. A 10 oz/yd² denim is about 10 × 33.906 ≈ 339 GSM.

What weights suit different garments?

Lightweight (<150 GSM) suits blouses and linings, mid-weight (150–300 GSM) suits shirts and dresses, and heavy (>300 GSM) suits denim, coats, and upholstery. Knits and wovens at the same GSM can drape very differently.

Why is fabric weight given per area, not per yard?

Bolt width varies (e.g. 44 in vs 60 in), so weight per linear yard depends on width while GSM (per square meter) is width-independent. Always compare fabrics by GSM or oz/yd² to judge true heft.

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Estimates for informational purposes only.

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This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

Fabric weight is the single most useful number for predicting how cloth will behave - how it drapes, how opaque it is, and whether your pattern was drafted for it. The trouble is that weight is quoted in three incompatible systems: GSM (grams per square metre, the global textile standard), oz/yd² (ounces per square yard, common in the US for shirting and apparel), and oz/linear yard (ounces per running yard at a stated width, used for denim and bottom-weight goods). This calculator converts between all three and then classifies the result on a lightweight-to-heavyweight scale. Because the linear-yard figure depends on how wide the bolt is, the tool asks for the fabric width whenever you enter or want that unit - a 12 oz/linear-yard denim at 44 inch is a very different cloth than the same 12 oz at 60 inch.

Formula / Method

The anchor conversion is 1 oz/yd² = 33.906 GSM (since 1 ounce = 28.3495 g and 1 yd² = 0.8361 m², the ratio is 28.3495 ÷ 0.8361). So GSM = oz/yd² × 33.906 and oz/yd² = GSM ÷ 33.906. For the linear-yard unit, one running yard at width W inches covers (36 × W) square inches = W÷36 square yards; therefore oz/yd² = oz/linear yard ÷ (W÷36), and the reverse multiplies back. The tool first reduces whatever you enter to GSM, then derives the other two units, using the width only where the linear measure is involved. Classification bands map GSM to descriptive ranges (under 100 very light, 100–150 light, 150–250 medium, 250–350 mid-heavy, 350–450 heavy, above 450 very heavy). A blank, zero, or negative weight - or a missing width when one is required - returns a friendly message.

Worked Example

A quilting cotton listed at 200 GSM converts to 200 ÷ 33.906 = 5.90 oz/yd², squarely medium weight. At a 44 inch bolt that is 5.90 × (44÷36) = 7.21 oz per linear yard. Going the other way, a 12 oz/linear-yard denim at 60 inch width: square yards per linear yard = 60÷36 = 1.667, so oz/yd² = 12 ÷ 1.667 = 7.20 oz/yd², and GSM = 7.20 × 33.906 = 244 GSM - lighter per square area than the "12 oz" label implies, because it is spread over a wide bolt. That width dependence is exactly why bottom-weight fabrics should be compared in oz/yd² or GSM, never raw linear ounces.

Common Mistakes

Comparing two fabrics by oz/linear-yard when they have different bolt widths - the wider one is lighter per area.

Confusing oz/yd² with oz/linear-yard; denim is usually quoted linear, shirting per square yard.

Using the wrong conversion constant - the correct factor is 33.906 GSM per oz/yd², not 28.35.

Forgetting to enter the fabric width when working in or to linear ounces, which makes that figure meaningless.

Treating weight as a proxy for thickness; a dense thin fabric and a lofty thick one can share a GSM.

Tips & FAQ

What weight do I need for my project? Roughly: 70–120 GSM for blouses and linings, 120–200 for shirts and dresses, 200–300 for trousers and structured garments, 300 GSM and up for jackets, bags, and upholstery. Why three units? History and industry - metric mills quote GSM, US apparel uses oz/yd², and denim/canvas mills price by the running yard. Does weight equal quality? No - a fine high-thread-count shirting can be light yet excellent; weight only predicts hand and opacity. How does width affect linear ounces? A heavier-sounding linear number on a wide bolt can be the same cloth as a lighter linear number on a narrow bolt; always normalise to per-area. What about knits? Knits are usually sold in GSM; jersey runs 140–220 GSM, interlock and ponte heavier. Will a heavier fabric hide my seams? Generally yes, but it also resists gathering and tight curves, so match weight to the pattern's recommended fabrics. Use this as a planning aid and confirm with a swatch before cutting a whole project.

Frequently Asked Questions

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