GSM to oz/yd² Calculator
Fabric weight between metric and imperial.
Convert fabric weight between grams per square metre and ounces per square yard, with a guide to what each weight is suitable for.
Converted weight
5.90 oz
200 gsm
The conversion is exact: an ounce is 28.3495 g and a square yard is 0.836127 m². Weight tells you what a fabric is for, not how good it is — a fine 120 gsm shirting can be far better cloth than a coarse 200 gsm one.
How the GSM to oz/yd² Calculator works
Fabric weight is quoted in grams per square metre almost everywhere except the United States, where it is ounces per square yard — and the conversion is exact rather than approximate, because both units are defined. One ounce per square yard is 33.906 grams per square metre, which is why a 10 oz denim and a 340 gsm denim are the same cloth.
Also known as: fabric weight converter · oz per square yard converter · GSM converter
An exact conversion, unlike most of this cluster
Both units are defined, so the conversion has no approximation in it. An ounce is 28.349523125 grams exactly, and a square yard is 0.83612736 square metres exactly. Dividing gives 33.906 grams per square metre for every ounce per square yard.
That is why a 10 oz denim and a 340 gsm denim are the same cloth, and why fabric specifications from American and European mills can be compared directly rather than approximately.
The units measure areal density — mass per unit area — which is independent of the fabric's width. Two bolts of the same GSM at different widths weigh different amounts per metre but are the same weight of cloth.
A worked example
A mill quotes 6 oz per square yard. Multiplying by 33.906 gives 203 gsm — a mid-weight fabric, suitable for a shirt or a light bottom-weight.
In the other direction, a 140 gsm jersey divided by 33.906 is 4.13 oz, which is a standard t-shirt weight. Knowing both figures is useful when a pattern specifies fabric in one system and the shop lists it in the other.
Where the answer misleads
Weight describes quantity of fibre, not quality. A tightly woven 120 gsm cotton with a long-staple yarn will outlast a coarse 200 gsm one, and will feel better doing it. Weight tells you what a fabric is for — drape, opacity, structure — rather than how good it is.
Knits are frequently quoted in grams per linear metre at a stated width, not per square metre, because they come off a tube and are sold by length. A figure that looks impossibly high for a jersey is usually linear; divide by the width in metres to compare.
Finally, the same GSM feels different in different fibres. A 200 gsm linen is airy and a 200 gsm polyester is not, because the fibre density and the weave structure both differ. Weight is one specification among several.
Frequently asked questions
What is the formula for GSM to oz/yd²?
Divide the GSM by 33.906. Going the other way, multiply the ounces by 33.906. The figure comes from an ounce being 28.3495 grams and a square yard being 0.836127 square metres.
What weight fabric do I need?
Roughly: under 100 gsm is a voile or lawn, 100 to 200 shirting and quilting cotton, 200 to 340 mid-weight bottoms and lighter denim, and above 340 heavy denim, canvas and upholstery. Jersey for t-shirts is usually 140 to 200.
Is a heavier fabric better quality?
Not on its own. Weight tells you how much fibre is in a square metre, not how good the fibre or the weave is. A fine 120 gsm shirting can be far better cloth than a coarse 200 gsm one; weight tells you what it is for, not how good it is.
Why do knits list weight differently?
Knits are often quoted in grams per linear metre at a stated width rather than per square metre, because they are sold by the length off a tube. Divide by the width in metres to get a comparable GSM.