The Japanese (Shakkanhō) Lengths equation converts lengths in Japanese units to modern (Western) lengths such as meters based on conversion conventions in place since 1891.
The base unit of length in the Shakkanhō system is the Shaku. The Shaku and its denominations are equivalent to the following metric measurements:
The equation also includes the Hiro (尋) used to measure depth. It is the same length as 1 Ken.
Since systems of romanizing Japanese have changed historically some of these measurements also have alternative names. The Ken is sometimes called the Japanese fathom or the Kin, whereas the Chō may be known as the Cho or Tsyo, and the Ri as the Li or Japanese mile.
Other Japanese units of measurement, such as those used for weight, may share the same names as the units used for length. Furthermore, since the Japanese language contains many homonyms some units for measuring area, volume, weight and mass, are romanized in the same manner as those above, but use different kanji (Chinese characters) to distinguish between them. One example is the Shaku, which when used to measure area is written with the character 勺.