Momme
Also: Monme, mom, もんめ
A Japanese unit of weight from the traditional shakkan system, used today mainly in the pearl trade and equal to exactly 3.75 grams.
The momme (Japanese: 匁, pronounced monme) is a traditional Japanese unit of weight from the shakkan system, equal to exactly 3.75 grams. In modern commerce the momme has kept a well-defined niche: it is the internationally most common unit of weight for cultured and natural pearls, especially in the Japanese and wider Asian pearl market.
Origin and historical context
The shakkan system was Japan's official system of measures and weights until the country moved to the metric system in 1891. Within it, the momme served as the base unit for precious-metal and jewellery weights. 160 momme traditionally made up one kin (600 g). During the nineteenth century the momme was carried into the Western world through the pearl trade, where it survives as an industry standard to this day.
Conversion table
| Unit | Value |
|---|---|
| 1 momme | 3.75 g |
| 1 momme | 57.870 troy grains |
| 1 momme | 2.411 pennyweight (dwt) |
| 1 momme | 0.1206 troy ounces |
| 1 momme | 0.1323 avoirdupois ounces |
| 10 momme | 37.5 g |
Role in the precious-metal and pearl trade
In precious-metal dealing the momme now plays only a minor part — here the troy ounce, the gram and the pennyweight dominate. The pearl market is different: loose pearls are often priced per momme. A pearl strand with a total weight of 10 momme therefore weighs 37.5 grams.
Anyone valuing historical Japanese silver or gold coins (for example ichibu-kin or isshu-gin) will also come across momme figures. To compute the melt value of such pieces correctly, converting to grams is the first step.
Formula box
Weight in grams = momme × 3.75
Weight in momme = grams ÷ 3.75
Using this conversion factor you can convert the current gold price per gram straight onto a momme basis — handy for valuing scrap or broken gold from the Asian market. Use the unit converter for quick conversions between momme, grams, pennyweight and other units.
Distinguishing it from similar units
The momme should not be confused with the Chinese tael (37.4–50.0 g depending on region) or the Indian tola (≈ 11.664 g). The Taiwanese tael happens to equal exactly 37.5 g, and thus 10 momme — though the common Hong Kong variant (37.429 g) differs. All three units spring from regional Asian precious-metal traditions and have survived in specific market segments, while the metric system governs everyday life.
In brief
The momme equals exactly 3.75 grams and today matters mainly in the pearl trade and in valuing historical Japanese precious-metal pieces. For a melt-value calculation, a simple multiplication by 3.75 is all it takes.