What GSM should curtain fabric be?

Most curtain fabric sits in the 200–300 g/m² band, heavy enough to hang in folds rather than flutter. Lighter cloth below 150 g/m² works for voiles and sheers where the point is light coming through; interlined curtains can go heavier still, because the interlining rather than the face fabric is doing the hanging.

Why does the same fabric have two different weights quoted?

Because one of them is per square yard and the other per running yard. Ounces per running yard weighs a yard of the roll at whatever width it happens to be, so a 60-inch roll gives a bigger number than a 45-inch roll of identical cloth. Only g/m² and oz/yd² compare two fabrics fairly.

What is momme, and why is silk measured in it?

Momme is the weight in pounds of a piece of silk 100 yards long and 45 inches wide, a unit the silk trade has kept for its own reasons. One momme is about 4.34 g/m², so 19 momme charmeuse is roughly 82 g/m². Because the width is fixed in the definition, momme does compare fairly — unlike ounces per running yard.

Does weight tell me how hard-wearing a fabric is?

Only loosely. Weight describes mass per area, not construction: a dense weave and a lofty one at the same weight behave completely differently, and abrasion resistance is measured separately by rub test rather than inferred from weight. Weight is a good guide to drape and to whether your machine will cope, and a poor guide to durability.

Fabric weight chart

Fabric weight falls into six working bands: under 80 g/m² is sheer, 80–120 is light, 120–200 medium, 200–300 heavy, 300–400 very heavy, and anything above that is upholstery and tarpaulin territory. Four units describe the same property — grams per square metre, ounces per square yard, ounces per running yard and momme — but only the first two describe the cloth alone. The other two depend on how wide the roll is.

The six weight bands

Weight is the fastest single description of a fabric you have not touched. It will not tell you how a cloth drapes or how long it lasts, but it will tell you within a band what the cloth is for and whether a domestic machine will sew it.

Weight bands, converted by the same ratios the calculator uses.
Band	g/m²	oz/yd²	Typical fabrics
Very light	0–80	0–2.4	Chiffon, organza, voile, fine lining. Sheer; needs care to sew.
Light	80–120	2.4–3.5	Lawn, batiste, shirting, quilting cotton, dress cotton.
Medium	120–200	3.5–5.9	Poplin, twill, jersey, linen, most dressmaking and quilting.
Heavy	200–300	5.9–8.8	Denim, drill, curtain fabric, light upholstery, bag fabric.
Very heavy	300–400	8.8–11.8	Upholstery weight, heavy canvas, outdoor fabric, coating.
Extra heavy	400+	11.8+	Heavy upholstery, tarpaulin, rug and carpet backing.

The boundaries are conventions rather than definitions, and different suppliers place them a few grams apart. What they are useful for is the middle of a band, not its edge: a fabric at 250 g/m² is unambiguously curtain and light-upholstery weight whoever is describing it, and a fabric at 199 g/m² is not meaningfully lighter than one at 201.

Four units for one property

The trade weighs cloth in four different units, and two of them are not measuring the same thing as the other two. This is the distinction worth carrying away from the page.

The four units, and what each actually describes.
Unit	Written	Describes
Grams per square metre	g/m²	The metric standard, and the only one that describes the cloth rather than the roll.
Ounces per square yard	oz/yd²	The US standard for most woven fabric.
Ounces per running yard	oz/yd	Used for denim and canvas. Depends on the roll width, so it says as much about the roll as the cloth.
Momme	mm	The silk unit: the weight in pounds of 100 yards by 45 inches.

Grams per square metre and ounces per square yard both measure mass over an area, so they compare any two fabrics fairly. One ounce per square yard is 33.906 g/m², exactly, and the conversion between them introduces no error of its own.

Ounces per running yard does not. It weighs a yard of the roll at whatever width the roll happens to be, so the number rises with the width even when the cloth is identical. Denim and canvas are sold this way, which is why a "12 oz denim" from two mills can be two different fabrics.

The same 200 g/m² cloth, weighed per running yard on three rolls.
Roll width	g/m²	oz per running yard
112 cm	200	7.23
137 cm	200	8.84
150 cm	200	9.68

One cloth, one weight, three different figures. Any running-yard weight quoted without a roll width beside it is incomplete, and the difference across common widths is more than a third.

Momme, and why silk is different

Momme is the silk trade's own unit: the weight in pounds of a piece 100 yards long and 45 inches wide. Because both dimensions are fixed in the definition, it behaves like an area weight rather than a running one and does compare two silks fairly. One momme is 4.3399 g/m², so 19 momme charmeuse is about 82.5 g/m² and 30 momme is about 130.2.

Habotai and lining silks run from 8 to 12 momme, charmeuse and crepe de chine from 16 to 22, and heavier dress and furnishing silks from 25 upwards. Below about 8 momme the cloth is sheer enough that its weight matters less than its weave.

What weight will not tell you

Three properties get read off a weight figure that it does not carry. Durability is the first: abrasion resistance is measured by rub test, and a tightly woven medium-weight cloth outlasts a lofty heavy one. Upholstery is specified in rubs rather than grams for that reason.

Drape is the second. Weight and stiffness are independent — a heavy silk falls in soft folds while a lighter cotton canvas stands up on its own. And shrinkage is the third: nothing about mass per area predicts how much a cloth moves in the wash. Wash a test piece and measure it, particularly on anything you intend to make to a fixed finished size.

Weight is a good guide to two practical things: whether the fabric suits the job in the table above, and whether your machine and needle will cope with it. To convert a figure between any of the four units, or to work the weight out from a swatch on a kitchen scale, use the fabric GSM calculator.

Common questions

What GSM should curtain fabric be?: Most curtain fabric sits in the 200–300 g/m² band, heavy enough to hang in folds rather than flutter. Lighter cloth below 150 g/m² works for voiles and sheers where the point is light coming through; interlined curtains can go heavier still, because the interlining rather than the face fabric is doing the hanging.
Why does the same fabric have two different weights quoted?: Because one of them is per square yard and the other per running yard. Ounces per running yard weighs a yard of the roll at whatever width it happens to be, so a 60-inch roll gives a bigger number than a 45-inch roll of identical cloth. Only g/m² and oz/yd² compare two fabrics fairly.
What is momme, and why is silk measured in it?: Momme is the weight in pounds of a piece of silk 100 yards long and 45 inches wide, a unit the silk trade has kept for its own reasons. One momme is about 4.34 g/m², so 19 momme charmeuse is roughly 82 g/m². Because the width is fixed in the definition, momme does compare fairly — unlike ounces per running yard.
Does weight tell me how hard-wearing a fabric is?: Only loosely. Weight describes mass per area, not construction: a dense weave and a lofty one at the same weight behave completely differently, and abrasion resistance is measured separately by rub test rather than inferred from weight. Weight is a good guide to drape and to whether your machine will cope, and a poor guide to durability.

Fabric weight chart

The six weight bands

Four units for one property

Momme, and why silk is different

What weight will not tell you

Common questions

Related tools

Fabric GSM calculator

Fabric width chart

Upholstery fabric calculator

Fabric width converter