Momme
Also: Monme, mom, もんめ
Japanese unit of weight from the traditional Shakkan system, today used primarily in the pearl trade and equal to exactly 3.75 grams.
The momme (Japanese: 匁, pronunciation: 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 internationally most widely used unit of weight for cultured and natural pearls, particularly in the Japanese and Asian pearl markets.
Origin and Historical Context
The Shakkan system was Japan's official system of weights and measures until the metric transition in 1891. The momme served as the base unit for precious metal and jewellery weights within that system. 160 momme traditionally made one kin (600 g). In the 19th century, the momme was exported to the Western world through the pearl trade, where it has remained the 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 |
Significance in Precious Metal and Pearl Trading
In the precious metals trade, the momme plays only a minor role today – here the troy ounce, gram, and pennyweight dominate. In the pearl market, however, loose pearls are frequently quoted at a momme price. A pearl necklace with a total weight of 10 momme therefore weighs 37.5 grams.
Those valuing historical Japanese silver or gold coins (e.g. Ichibu-kin, Isshu-gin) also encounter momme specifications. For the correct calculation of the melt value of such pieces, converting to grams is the first step.
Formula Box
Weight in grams = Momme × 3.75
Weight in momme = Grams ÷ 3.75
The current gold price per gram can be converted directly to a momme basis using 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 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 coincidentally equals exactly 37.5 g and thus 10 momme – however, the more common Hong Kong variant (37.429 g) differs. All three units originate from regional precious metal traditions in Asia and have survived in specific market segments, while the metric system dominates everyday use.
In Brief
The momme equals exactly 3.75 grams and is today primarily relevant in the pearl trade and for valuing historical Japanese precious metal pieces. For melt value calculations, a simple multiplication by 3.75 suffices.