Bone Weight

Bone weight (cheng gu) is a folk method of reading a birth by table lookup. Each part of the lunar birth date — year, month, day and hour — is given a bone weight; the four are added together, and the total points to a four-line verse. Because it needs only a lookup and a sum, with no chart and no five-element analysis, it was traditionally sold as fortune telling anyone could do unaided.

Origins: attributed to Yuan Tiangang

The method is usually credited to the early Tang physiognomist Yuan Tiangang, but the official histories give no support for this:

• The Old Book of Tang says he was especially skilled at physiognomy, but says nothing of bone weight.
• A phrase about flesh and bone in the New Book of Tang comes from his reading of a face and has nothing to do with this method.
• The History of Song lists his works without it.

It is best understood as a later attribution, passed down as a section of popular almanacs and fortune-telling handbooks. The Hong Kong almanac Tung Shing still prints a bone-weight page.

How it works: four tables, one sum

• Year: weighed by its place in the sixty-year cycle, from 5 qian to 1 liang 9 qian.
• Month: the lunar month, from 5 qian to 1 liang 8 qian.
• Day: the lunar day, 1st to 30th, from 5 qian to 1 liang 8 qian.
• Hour: the twelve two-hour periods, from 6 qian to 1 liang 6 qian.

The units are the liang and the qian; one liang is ten qian.

A worked example (taken from a circulating version's own example): born on lunar New Year's Day 1971, in the first two-hour period.

• Year: Xin Hai, 1 liang 7 qian
• Month: first month, 6 qian
• Day: 1st, 5 qian
• Hour: Zi, 1 liang 6 qian
• Total: 4 liang 4 qian

The verse for 4 liang 4 qian, in Guanyitang's own translation:

All things rest with heaven, so do not strain to seek them; know that fortune depends on how a person cultivates it. In the prime years wealth rarely goes as wished, but the later years bring gladness and an end to worry.

Only fifty-one weights

Working through every combination of the four tables, the total can only fall between 2 liang 1 qian and 7 liang 1 qian — fifty-one steps with no gaps. The most common is 3 liang 9 qian, about five per cent of all combinations.

Many sites list a verse for 7 liang 2 qian, but by the tables it cannot occur; it is generally thought to be a later addition.

Where calculators disagree

Traditions differ on a few points, so the rules need to be settled first:

• When the year turns: most bone-weight texts use lunar New Year's Day, while some calculators borrow BaZi's start of spring. For births between the two, the year differs.
• Leap months: a common rule counts up to the 15th as that month and from the 16th as the next.
• After 11 pm: the first two-hour period begins at 11 pm, and whether that hour belongs to the same day or the next changes the day's weight.
• Unknown hour: the hour changes the result, so it should not simply be assumed.

Guanyitang's bone weight tool picks one reading for each and also shows the result under the other.

Versions and variants

No early edition of the verses survives in a form that can be cited. The versions in circulation belong to several lines of transmission and differ, sometimes in meaning: in the verse for 6 liang 8 qian, one line has the family foundation as "a boat upon the water", another as "lasting a thousand ages". The tables differ too; the Gui Hai year is given as 6 qian in some versions and 7 in others.

Guanyitang compared independent versions word by word and took the majority reading, publishing every variant and decision in sources and variants.

What it can tell you

The lighter weights' verses mostly describe hardship and the heavier ones wealth and office, measured by the values of an older society; some old notes even state a lifespan, which we leave out entirely. It is a way to learn about a widespread folk practice, not a judgement of anyone's life. For a detailed look at your own chart, cast a full BaZi.

FAQ

Did Yuan Tiangang really invent it?

There is no evidence that he did. The Old Book of Tang says he was especially skilled at physiognomy but never mentions bone weight; a phrase about flesh and bone in the New Book of Tang comes from his reading of a face and has nothing to do with this method; and the History of Song lists his works without it. The attribution came later. The method was passed down as a section of almanacs and fortune-telling handbooks, and the Hong Kong almanac Tung Shing still prints a bone-weight page.

Does a heavier weight mean a better fate?

No. Broadly, the lighter weights' verses describe hardship and the heavier ones wealth and office, but that reflects the values of an older society, not a judgement of anyone's life; countless people share each weight, yet each weight has a single verse. It is a window onto a popular tradition. For a detailed look at your own chart, cast a full BaZi.

Why is there no 7 liang 2 qian?

By the tables, the four weights add up to at most 7 liang 1 qian, so 7 liang 2 qian cannot occur. Many versions include a verse for it anyway; it is generally thought to be a later addition.

Can I use it without knowing my birth hour?

The hour contributes between 6 qian and 1 liang 6 qian, so it changes the total and the verse. Please don't simply assume noon; check a birth record or ask family first. If there is no way to find out, treat the result as a rough reference only.

References

• Old Book of Tang, chapter 191, biography of Yuan Tiangang (Wikisource)
• New Book of Tang, chapter 204 (the phrase about flesh and bone concerns physiognomy)
• History of Song, chapter 206, bibliography (Yuan Tiangang's listed works do not include bone weight)
• Guanyitang bone weight corpus chenggu-v1: four independent versions compared word by word; variants at /chenggu/sources