Convert Chi (Chinese Foot) to kilometres

The modern market chi

China's metrication programme did not abolish traditional units so much as redefine them against the metre. The market system, or shizhi, fixed the chi at exactly one third of a metre — 33.333 centimetres — the jin at 500 grams and the mu at 666.67 square metres. Because these are exact metric fractions rather than approximations of older values, conversions in modern Chinese contexts are unambiguous.

This is why the chi still appears in fabric shops, tailoring, furniture and traditional architecture: it was made compatible with the metric system rather than displaced by it. A bolt of cloth quoted in chi in a Guangzhou market converts exactly, with no regional variant to check.

Historical values and why they matter

Before the twentieth-century standardisation, the chi tracked dynastic reform. Archaeological rules and standard measures give roughly 23.1 centimetres for the Zhou and Han period, around 31 centimetres for the Tang and Song, and about 32 centimetres in Qing practice. The unit grew by nearly forty per cent over two millennia.

For anyone reading a classical text, a temple inventory or an archaeological report, this means the modern one-third-metre value is simply wrong. A Han dynasty measurement of ten chi is about 2.31 metres, not 3.33 metres — a difference large enough to change the reconstructed size of a building or the interpretation of a described object.

The chi outside mainland China

Taiwan and Hong Kong carried forward measures from a different lineage. Hong Kong's traditional chi, standardised under colonial ordinance, is 371.475 millimetres, and it is still used in property and construction contexts alongside metric and imperial figures. Japanese and Korean feet — the shaku and the ja — derive from the same East Asian family and sit near 30.3 centimetres.

A document from any of these jurisdictions therefore needs its origin identified before a factor is chosen. The characters are shared across the region; the values are not, and the spread between the mainland market chi and the Hong Kong chi is over ten per cent.

Working with chi in practice

For contemporary mainland use, apply the exact one-third-metre factor and stop. For historical work, cite the dynasty and the archaeological or textual authority for the value used, and treat the result as an estimate with a range rather than a point value. For Hong Kong and Taiwan, use the local statutory figure.

The sub-unit chain is consistent everywhere: ten cun to the chi, ten fen to the cun, and ten chi to the zhang. That decimal structure is one of the oldest in world metrology and it means a chi error propagates cleanly by powers of ten rather than through awkward fractions — which is convenient for arithmetic and dangerous for proofreading, because a misplaced decimal looks plausible.

One further check is worth building into any workflow that mixes eras: state the assumed value in the output, not only in the working. A note that reads "10 chi ≈ 3.33 m (modern market chi)" survives being copied into another document, while a bare metric figure does not. Most of the contradictory chi conversions circulating online are not disputes about the evidence at all — they are correct answers to different questions that lost the label identifying which question they answered.

Common mistakes to avoid

• The modern mainland chi is exactly 1/3 m; do not apply that value to pre-modern texts.
• Hong Kong's statutory chi is 371.475 mm, over ten per cent longer than the mainland market chi.
• Han-era chi is close to 23 cm — using the modern value inflates ancient dimensions by more than forty per cent.

Questions people ask about the Chi (Chinese Foot)

How long is one chi?

In mainland China today, exactly one third of a metre, or 33.333 centimetres. Hong Kong's traditional chi is 371.475 millimetres, and historical Chinese values range from about 23 to 32 centimetres depending on dynasty.

Is the chi still used in China?

Yes. The market system that defines it was retained through metrication, so the chi remains common in textiles, tailoring, furniture and traditional architecture, with an exact metric equivalent.

How does the chi relate to the cun and the zhang?

The system is decimal: ten cun make one chi, and ten chi make one zhang. Below the cun, ten fen make one cun.