Tai Xi (Fetal Breath): the appendix row called Xi, and what it can and cannot do
Tai Xi (“Fetal Breath”, the appendix row is labeled “Xi”) is a stem-branch pair derived from the day pillar. The day stem pairs with the stem that forms a Five Combination with it: Jia with Ji, Yi with Geng, Bing with Xin, Ding with Ren, Wu with Gui. The day branch pairs with the branch that forms a Six Harmony with it: Zi with Chou, Yin with Hai, Mao with Xu, Chen with You, Si with Shen, Wu with Wei. For example, a Yi Mao day gives Geng Xu, and a Ding Mao day gives Ren Xu. Our site lists it in the “Life Palace, conception pillar and Growth tables” of the chart result, under the label “Xi”, beside the Conception Pillar (Tai Yuan) and the Life Palace. It is traditional reference only: not a fifth pillar, not in the strength score, and it never changes favorability.
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At a glance
| Piece | Rule | On a Yi Mao day |
|---|---|---|
| Day stem | Take the stem that forms a Five Combination: Jia–Ji, Yi–Geng, Bing–Xin, Ding–Ren, Wu–Gui | Yi pairs with Geng |
| Day branch | Take the branch that forms a Six Harmony: Zi–Chou, Yin–Hai, Mao–Xu, Chen–You, Si–Shen, Wu–Wei | Mao pairs with Xu |
| Result | One stem and one branch: the Tai Xi | Geng Xu |
| Ten God of the stem | Yang Day Master: Direct Wealth; yin Day Master: Direct Officer | Yi is yin, so Direct Officer |
| Status | Appendix reference, not a fifth pillar | Shown in the row labeled “Xi” |
- Tai Xi (“Fetal Breath”)
- A stem-branch pair derived from the day pillar by Five Combination of stems and Six Harmony of branches
- Conception Pillar (Tai Yuan)
- A separate appendix pair derived from the month pillar, not from the day pillar
- Life Palace
- Another appendix position in the chart result, read as reference
- Five Combinations of stems
- The five fixed stem pairs: Jia–Ji, Yi–Geng, Bing–Xin, Ding–Ren, Wu–Gui
- Six Harmonies of branches
- The six fixed branch pairs: Zi–Chou, Yin–Hai, Mao–Xu, Chen–You, Si–Shen, Wu–Wei
Two real charts
Ding Wei (丁未) · Ren Yin (壬寅) · Yi Mao (乙卯) · Gui Wei (癸未) (male, Feb 20, 1967, 13:45, Beijing)
This chart has no Metal at all, and its Tai Xi is Geng Xu, a Metal pair the natal chart does not hold. True solar time was 13:16, and the 1967 Li Chun had passed, so the year pillar is Ding Wei and the month pillar Ren Yin. The Day Master is Yi Wood, born in a Yin month; the main qi of Yin is Jia Wood, Rob Wealth, so the month command supports the Day Master. The stems are Ding Eating God, Ren Direct Resource and Gui Indirect Resource. The branches are Wei Indirect Wealth, Yin Rob Wealth, Mao Companion and Wei Indirect Wealth.
The scoring gives Companions 2.35, Resource 2, Output 1.55, Wealth 1.1 and Officer/Killings 0, and the chart is strong (month support; support 4.35, pressure 2.65). Useful element Fire (Output), favorable Metal and Earth, unfavorable Wood. Tai Xi is Geng Xu, from Yi pairing with Geng and Mao pairing with Xu; the Conception Pillar is Gui Si.
The Geng Metal on the appendix is a hint, not a natal Officer. The chart's Officer/Killings score stays at 0, because we do not add Tai Xi to the four pillars. Metal only becomes real when a Luck Pillar or an Annual Pillar brings it. Until then, the chart is read as strong Yi Wood that wants Fire Output, with Metal and Earth favorable.
Bing Chen (丙辰) · Ji Hai (己亥) · Ding Mao (丁卯) · Gui Mao (癸卯) (female, Nov 11, 1976, 06:30, Beijing)
Here both Tai Xi elements are in the unfavorable column, and the chart's reading does not move. True solar time was 06:30, and that year's Start of Winter had passed, so the month pillar is Ji Hai. The Day Master is Ding Fire, born in a Hai month; the main qi of Hai is Ren Water, Direct Officer. The stems are Bing Rob Wealth, Ji Eating God and Gui Seven Killings. The branches are Chen Hurting Officer, Hai Direct Officer, Mao Indirect Resource and Mao Indirect Resource.
The scoring gives Resource 2.82, Officer/Killings 2.38, Output 1.3, Companions 0.5 and Wealth 0, and the chart is weak (support 3.32, pressure 3.68). Useful element Wood (Resource), favorable Fire, unfavorable Water and Earth. Tai Xi is Ren Xu, from Ding pairing with Ren and Mao pairing with Xu; the Conception Pillar is Geng Yin.
Ren Water is Direct Officer and Xu Earth is Hurting Officer, and both elements are unfavorable here. That still does not change the chart. Tai Xi does not enter the scoring, so the weak Ding Fire still takes the two Mao Wood Resource characters as its Useful element and still welcomes Fire. The appendix pair is a note beside the chart, not a weight on it.
Data: how often Tai Xi changes anything
The appendix row matched the derivation on all 2,000 charts, which is expected from a fixed rule. The Ten God on the stem is fixed too: the 983 yang-stem Day Masters all had Direct Wealth, and the 1017 yin-stem Day Masters all had Direct Officer.
In the 1898 non-special charts, the stem element was Useful 10.7%, favorable 35.8% and unfavorable 36.9%; the branch element was Useful 17.8%, favorable 35.7% and unfavorable 33.6%. At least one of the two was favorable or useful in 71.9%, and both were unfavorable in 13%.
New elements are the exception. Tai Xi brought an element absent from the natal chart in 146 charts, 7.7%, and 67.1% of those new elements were favorable or useful. Its stem was already on a natal stem in 26.2%, and its branch was already on a natal branch in 22.8%.
Overlaps with the natal chart and the appendix are small. Tai Xi matched one of the four pillars in 4.4%, matched the Conception Pillar in 1.6%, and its branch was in a six clash with a natal branch in 22.3%.
Simulated charts: our BaZi calculator generated 2,000 random birth times (birth years 1950–2010 uniformly random, random birth time, half male/half female, Beijing true solar time), cast each chart and judged strength and the Useful element by traditional rules, then counted the results. These are simulated results, not a survey of real people and not a measure of prediction accuracy. Tai Xi was derived from the day stem by Five Combination and the day branch by Six Harmony and checked against the appendix row labeled “Xi”; its Ten God, element favorability, new elements, overlaps and clashes were tallied across the set, with special structures excluded where favorability was compared. Calculation version: our BaZi calculator after the Oct 15, 2026 update (the same rules the site uses now; rechecked with site version v73 on Oct 20, 2026), random seed 20261014. To reproduce: rerun the same version with the same seed and the results match exactly; you can check any single chart by entering the same birth time in our BaZi calculator.
The rule: combine the day stem, harmonize the day branch
Tai Xi is built from one fixed move on each half of the day pillar. The day stem changes to the stem it forms a Five Combination with, and the day branch changes to the branch it forms a Six Harmony with. No season, no strength and no other pillar enters the calculation.
Two examples make the pattern clear. A Yi Mao day becomes Geng Xu, because Yi pairs with Geng and Mao pairs with Xu. A Ding Mao day becomes Ren Xu, because Ding pairs with Ren and Mao pairs with Xu. Every chart has exactly one Tai Xi, and it is listed in the “Life Palace, conception pillar and Growth tables” under “Xi”.
The Ten God on the stem is fixed by polarity
The Tai Xi stem is not a random addition: its Ten God is set by the Day Master's polarity. A yang Day Master, Jia, Bing, Wu, Geng or Ren, always gets Direct Wealth on the Tai Xi stem. A yin Day Master, Yi, Ding, Ji, Xin or Gui, always gets Direct Officer.
The 2,000 charts show no exception. There were 983 yang-stem Day Masters, all with Direct Wealth, and 1017 yin-stem Day Masters, all with Direct Officer. That is a property of the derivation, not a finding about any person.
Most of the time it repeats elements already in the chart
Tai Xi usually rearranges what the chart already has. It brought an element absent from the natal chart in 146 charts, 7.7%. Its stem was already among the natal stems in 26.2%, and its branch was already among the natal branches in 22.8%.
When it does add something new, that element is often welcome. In the 146 charts with a new element, 67.1% had that element favorable or useful. That is a tendency, not a promise, because the element still has to fit the chart's strength and climate.
Overlap with other appendix positions is small. Tai Xi was identical to the Conception Pillar in only 1.6% of charts and identical to one of the four pillars in 4.4%. Its branch was in a six clash with a natal branch in 22.3%.
Favorable or not: no lean either way
Tai Xi leans neither way on favorability. In the 1898 non-special charts, the Tai Xi stem element was Useful 10.7%, favorable 35.8% and unfavorable 36.9%. The branch element was Useful 17.8%, favorable 35.7% and unfavorable 33.6%.
At least one of the two was favorable or useful in 71.9% of charts, and both were unfavorable in 13%. The stem was favorable (35.8%) about as often as unfavorable (36.9%). There is no sign that Tai Xi is inherently a blessing or a curse.
On our site: an appendix row, outside the count
We list Tai Xi beside the Conception Pillar and the Life Palace, and we stop there. It is not a fifth pillar, it does not join the strength points, and it does not edit the favorable and unfavorable lists. The chart is read from the four pillars, the month command and the Useful element.
The practical reason is that the rule never looks at the season or the other pillars. It is fixed by the day pillar alone, so it cannot say how strong the Day Master is; that is the job of the four pillars and the month command. Even when it brings something new, the Useful element test still decides whether that element matters.
FAQ
How is Tai Xi calculated, and what is mine?
Take the stem that forms a Five Combination with your day stem, and the branch that forms a Six Harmony with your day branch. Jia pairs with Ji, Yi with Geng, Bing with Xin, Ding with Ren, Wu with Gui; Zi pairs with Chou, Yin with Hai, Mao with Xu, Chen with You, Si with Shen, Wu with Wei. Our site shows the result in the “Life Palace, conception pillar and Growth tables” under “Xi”. A Yi Mao day gives Geng Xu.
What is the difference between Tai Xi and the Conception Pillar?
The Conception Pillar is derived from the month pillar, while Tai Xi is derived from the day pillar. Both appear in the same appendix and both are reference only. They were identical in 1.6% of the 2,000 charts. Neither enters strength or favorability.
What does Tai Xi represent, and does it affect my fate?
Traditionally it is read as a small image of the prenatal state, which is why the name means Fetal Breath. On our site it is a reference line only: it does not enter the strength score and does not change the Useful element or favorability. In 7.7% of charts it brought an element the chart did not have, and even then the Useful element test decides what that element means.
Does Tai Xi combining with the day pillar mean my marriage will be good?
No single factor decides a marriage. The combination is part of how Tai Xi is built, so every chart has it, which means it cannot tell one relationship from another. A marriage depends on the whole chart, the two people and their choices. Read Tai Xi as a note, not as a verdict.
Common view vs. our view
| Common view | Our view | Why |
|---|---|---|
| Tai Xi shows your prenatal constitution and is very accurate | It is appendix reference, and its derivation leaves no room for variation | The pair is fixed by the day pillar alone, and it brought a new element in only 7.7% of charts |
| Tai Xi is a fifth pillar and should be counted in strength | It does not enter the score and does not change favorability | Example 1 has Officer/Killings 0; a Geng Metal Tai Xi does not give it an Officer |
| Tai Xi combines with the day pillar, so the marriage will be good | The combination is part of the derivation, so every chart has it | Yang Day Masters always get Direct Wealth and yin Day Masters always get Direct Officer, with no exceptions in 2,000 charts |
| A Tai Xi with an unfavorable element is a bad sign | Both elements were unfavorable in only 13% of charts | At least one was favorable or useful in 71.9%, and it never enters the score |
Common mistakes
- Tai Xi is the state at conception and can be read like a fifth pillar: it is derived from the day pillar by fixed rules and stays in the appendix; it is not a fifth pillar and does not enter strength.
- Tai Xi adds an element the chart is missing: it brought a new element in 146 charts, 7.7%; most of the time it repeats elements already present.
- A Tai Xi that combines with the day pillar means a good marriage: the combination is built into the derivation and appears in every chart, so it cannot separate one marriage from another.
- An unfavorable Tai Xi spoils the chart: both of its characters were unfavorable in 13% of charts, and since it never enters the score, the natal reading stands.