units & tech: Mu - 畝 Bu - 步 Chi

domingo, 16 de noviembre de 2025

Mu - 畝 Bu - 步 Chi - 尺

Some weeks ago, I was reading a Chinese article translated into English about agriculture, that mentioned the area of a parcel in mu : "... It involves an investment of 60 million yuan ($9.3 million) and takes up an area of 62 mu (4.13 hectares). ..."

In this part of the world this is an unknown measure unit, and investigating I found that is still valid in China as secondary versus the International Systems of Units; something like the acres in some anglosaxon countries.

The mu ( 畝 ) , is a traditional Chinese unit of measurement for land area, that originally was defined in terms of square bu, being bu another old measure unit equivalent to "steps". Mu has had different values according the place where is located that parcel.

The bu ( 步 ) , was a tradicional Chinese unit of measurement for lenght, and was defined in terms o another unit, the chi.

The chi ( 尺 ), that was another old chinese measure unit for lenght, derived from the distance measured by a human hand of an adult woman. 10 chi equal to 1 zhang ( 丈 ). And is known that existed 3000 years ago in the Chinese Yin dinasty, and was spreadly used in the east Asia cultures such as Japan, Korea or Vietnam.

The value of this old measure units varied in different locations, cultures, and countries, and also throughout the years. For example, before the Three Kingdoms era, "100 bu make a bu", but changed to "240 bu make a mu".

A rural place in Yunnan (China) - From a Youtube video of Jabiertzo

Using an iron rule of the Han dinasty ( a chi aproximately to 23'1 cm ), a mu in the Qin and Han dinasties was calculated aproximately by:

240 bu² = 240 ( 6 chi / bu × 0,231 m/ chi ) ² ≈ 461 m² ≈ 0,6916 mu

There were also many other measure units related, most of them now are deprecated. For example, in January 1915, the goverment promulgated a measurement law to use not only the metric system as the standard, but also a set of Chinese measurement units and equivalency. Or, in February 1929, another act, and in 1930 many equivalencies were revised.

In mainland China, since the promulgation in 1959 of the "Decree of the State Council Concerning the Use of Uniform Legal Measures in the Country", the traditional Chinese measurement system was discontinued, and the mu is the only area unit retained. That decree stipulated that 1 mu is equal to 60 square zhang, which is approximately equal to 666,67 m² , 15 mu equal to 1 hectare, and 1 km² equal to 1500 mu.

15 mu ≈ 1 ha = 10000 m² (In mainland China, since 1959)

1 mu ≈ 60 zhang² ≈ 666'67 m² (In mainland China since 1959)

There were many related measure units in mainland China, Korea, Honk Kong, Macau, Japan, Taiwan, ... that can be found in old literature.

In the case of the mentioned article in news: 62 mu = 62 * 666'67 m²/mu = 41333'54 m² ≈ 4'13 ha .