Momme
Also: Monme, mom, もんめ
Japanese unit of weight from the traditional Shakkan system, today used 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 and equals exactly 3.75 grams. In modern trade the momme has retained a clearly defined niche: it is the most internationally common unit of weight for cultured pearls and natural pearls, especially in the Japanese and Asian pearl market.
Origin and historical context
The Shakkan system was the official Japanese system of measures and weights until the metric transition in 1891. The momme formed the base unit there for precious-metal and jewellery weights. 160 momme traditionally made up one kin (600 g). In the 19th century the momme was exported to the Western world via the pearl trade, where it has survived as an industry standard to this day.
Conversion table
| Unit | Value |
|---|---|
| 1 momme | 3.75 g |
| 1 momme | 57.870 troy grain |
| 1 momme | 2.411 pennyweight (dwt) |
| 1 momme | 0.1206 troy ounces |
| 1 momme | 0.1323 avoirdupois ounces |
| 10 momme | 37.5 g |
Significance in the precious-metal and pearl trade
In the precious-metal trade the momme today plays only a subordinate role – here the troy ounce, the gram and the pennyweight dominate. It is different in the pearl market: loose pearls are frequently assigned a momme price there. A pearl necklace with a total weight of 10 momme accordingly weighs 37.5 grams.
Anyone valuing historical Japanese silver or gold coins (e.g. ichibu-kin, isshu-gin) also encounters momme figures. For the correct calculation of the melt value of such pieces, conversion into grams is the first step.
Formula box
Weight in grams = momme × 3.75
Weight in momme = grams ÷ 3.75
You can convert the current gold price per gram directly onto a momme basis with this conversion factor, for example when valuing scrap gold or broken gold from the Asian region. Use the unit converter for quick conversions between momme, grams, pennyweight and other units.
Distinction from similar units
The momme is not to be confused with the Chinese tael (37.4–50.0 g depending on the region) or the Indian tola (≈ 11.664 g). The Taiwanese tael coincidentally equals exactly 37.5 g and thus 10 momme – the widespread Hong Kong variant (37.429 g), however, deviates. All three units stem from regional precious-metal traditions of Asia and have survived in specific market segments, while the metric system dominates everyday life.
In brief
The momme equals exactly 3.75 grams and is today relevant above all in the pearl trade as well as in the valuation of historical Japanese precious-metal pieces. For melt-value calculation, simple multiplication by 3.75 suffices.