Silk momme: what is it, and how do you calculate it?

Momme (abbreviated mm) is the unit used to weigh silk. It tells you how much a square metre of fabric weighs, at about 4.34 g/m² per momme, so a 16 momme silk weighs nearly 70 g/m². It is a weight, not a quality label, and it takes two divisions to work out.

Silk pillowcases made the word famous, with their “19”, “22” or “25 momme”. Our product pages give the weight another way, in g/ml: the weight of one metre of fabric across its full width. To compare one of our silks with a pattern or a shop that thinks in momme, you need to get from one to the other.

A Japanese word, an English definition

Momme comes from the Japanese monme, a unit of mass fixed at 3.75 g since the Meiji era. It has outlived silk, too: in Japan, cultured pearls are still traded by the momme.

For silk, the word took on another meaning. It is defined as the weight, in pounds, of a piece 45 inches wide and 100 yards long. Converted, that gives 453.6 g for 104.5 m², or 4.34 g/m² per momme. And “mm” has nothing to do with millimetres. A 19 mm satin is not 19 millimetres thick.

How do you calculate momme?

It all starts from the weight per square metre. If you know it, one division is enough. If it is given in g/ml, as on our pages, you need two.

momme = g/m² ÷ 4.34
momme = g/ml ÷ width in metres ÷ 4.34

From our product pages to momme

Take some of our plain crepes de Chine, listed at 87 g/ml on a 130 cm width. Only some of them, because the weight varies from one reference to the next, even within a type, so always start from the page of the fabric you have in mind.

1. Write the width in metres: 130 cm is 1.30 m.
2. Divide the weight by the width: 87 ÷ 1.30 = 66.9 g/m².
3. Divide by 4.34: 66.9 ÷ 4.34 = 15.4, so about 15 momme.

When the page gives a range, 135–140 cm or 110–115 g/ml, take the middle. The difference stays well under one momme, which no hand will ever feel.

The other way round, when a pattern asks for 19 momme

Multiply by 4.34 to get back to g/m², then by the width to get g/ml. 19 × 4.34 gives 82.5 g/m², and on a 140 cm width, 82.5 × 1.40 gives 115 g/ml. Two of our plain silk satins sit either side of that figure: the white one, at 105 g/ml on 135–140 cm (about 18 momme), and the buttercup yellow, at 122 g/ml on 140 cm (about 20). With the same weave, those few extra grams mean a little more body and opacity.

4.34 or 4.3056?

You will also come across this second factor at some silk sellers, though we have not found anywhere where it comes from. The QUDT units vocabulary, which lists units of measure and their conversions, gives 4.340 g/m² per momme, which is also what the definition works out to. The gap is under 1%: 19 momme weigh 82.5 g/m² one way and 81.8 the other. For sewing, it makes no difference.

Nathalie’s tip: keep an offcut of every silk you have enjoyed sewing, with its momme pencilled on a label. The day you order without touching, “like that crepe, but a little heavier” will turn into a number.

The momme of our silks

Each row is one specific silk, because weights vary from one reference to the next (our triple organzas, for instance, range from 112 to 128 g/ml depending on colour and width). The values are rounded. Anything finer would be false precision.

Look at the ivory taffeta and the lime green crepe de Chine, both at 15 momme. The taffeta rustles and holds a fold like a sheet of paper, while the crepe de Chine runs through your fingers. Same with the dupion and the satin, one momme apart. Momme tells you how much silk there is per square metre; the weave, meaning the way the threads cross, decides almost everything else.

Is more momme better?

Not necessarily.

On a pillowcase washed every week, more momme means more silk, so a more opaque, longer-lasting fabric. Hence the 22 and 25 momme on pillowcases. For a garment, the right number depends on what you want from the fabric, and a floaty blouse would gain nothing from weighing twice as much.

For a fluid blouse, we prefer crepe de Chine around 15 momme, heavy enough not to be see-through and more biddable under the presser foot than a satin. A bias-cut dress calls for a satin of 18 to 20, which follows the body. For volume, it is no longer the weight that counts but the body of the cloth: dupion and taffeta hold a pleated skirt where a heavier satin would collapse. At the other end of the table, organza and its 5 momme more often support a garment than make it.

And for other fabrics?

Momme is a silk thing. For cotton, linen or wool, weights are given in g/m² or g/ml. Some polyester satins do quote momme, though. The number then gives a weight, nothing more, and says nothing at all about the fibre.

Next time a pillowcase promises 25 momme, you will know what that weighs: about 108 g/m². For everything else, a sample will always tell you more than a number, and our team can advise you on the weight and the length of fabric your project needs.

Happy sewing,
Nathalie