Four Pillars

Four Pillars Bazi Chart

Enter your Gregorian birth date and time to derive the year, month, day and hour pillars, and list the Ten Gods, hidden stems, Na Yin, empty phases, Five Elements distribution and eight Luck Pillars.

This tool bounds the year pillar at the Beginning of Spring and the month pillar at the twelve solar terms, and switches the day at 23:00, following the common conventions of modern charting. All times are taken as Beijing time (UTC+8) by default, with optional true solar time correction. Bazi belongs to folk culture; the result is for self-reflection and entertainment only.

Enter birth data

Use the Gregorian (Western) date; this tool supports 1900 to 2100.

Use the 24-hour clock for hours and minutes. Each two-hour period is one earthly-branch hour.

Gender only decides whether the Luck Pillars run forward or backward.

Advanced options

Beijing time is the standard time at 120°E. If you were not born on the 120° meridian, the real sun position differs from the clock; enabling this converts to true solar time from longitude and the equation of time.

Fill in the birth date and time, then press "Cast chart" to get your Four Pillars chart.

Bazi has no scientific predictive power; the result is for self-reflection and entertainment only.

How is Bazi cast? The Four Pillars, Ten Gods, hidden stems and Luck Pillars explained

What is Bazi

Bazi (also called the Four Pillars or birth Bazi) pairs each of the year, month, day and hour of birth with a stem-branch pair, making four pairs and eight characters that describe a person's chart. Each pillar is made of a heavenly stem (ten characters: Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui) and an earthly branch (twelve characters: Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai).

Stem-branch day counting goes back to the Shang dynasty, cycling in units of sixty (the sexagenary cycle); applying stem-branch to the four layers of year, month, day and hour gradually settled after the Han dynasty. The year and month follow the solar terms, not the lunar calendar — this is the most common beginner mistake, and the reason this tool prints the exact solar-term moments in the result.

How each pillar is determined

Pillar Basis Common mistake
Year Beginning of Spring. Born before it, the year pillar counts as the previous year Assuming the year changes on New Year's Day or the lunar new year
Month Twelve solar terms (Beginning of Spring, Awakening of Insects, Pure Brightness, Beginning of Summer, Grain in Ear, Minor Heat, Beginning of Autumn, White Dew, Cold Dew, Beginning of Winter, Major Snow, Minor Cold) Assuming the month changes on the lunar first of the month
Day Continuous sexagenary day count; this tool switches the day at 23:00 (late Zi hour goes to the next day) Assuming the day changes at midnight 00:00
Hour One earthly-branch hour is two hours; Zi hour is 23:00-00:59 Assuming the hour starts on the hour

Solar terms are positions of the sun on the ecliptic — a single global instant — so the year and month boundaries do not depend on the birthplace; the hour, however, is a local time concept, which is exactly what true solar time correction handles.

The Five Tigers and Five Rats

The stem of the month pillar and the stem of the hour pillar are not free choices; they are derived from the year stem and the day stem:

Five Tigers (year stem determines the Yin-month stem)

Year stem Jia, Ji Yi, Geng Bing, Xin Ding, Ren Wu, Gui
Yin-month stem Bing Wu Geng Ren Jia

Once the Yin month is set, the rest follow the stem order.

Five Rats (day stem determines the Zi-hour stem)

Day stem Jia, Ji Yi, Geng Bing, Xin Ding, Ren Wu, Gui
Zi-hour stem Jia Bing Wu Geng Ren

Once the Zi hour is set, the rest follow the stem order.

What are the Ten Gods

The Ten Gods are read from the stem of the day pillar (called the Day Master or Day Element) as the center, looking at the relation between other stems and the Day Master. The relation is decided by two things: the Five Elements generation and control, and whether the polarity (yin/yang) matches. The same relation gets a different name for same versus opposite polarity:

Relation to Day Master Same polarity Opposite polarity
Same as me (same element) Friend Robber
I generate Food Officer-Hurt
I control Wealth-Indirect Wealth-Direct
Controls me Killer Officer-Direct
Generates me Seal-Indirect Seal-Direct

The Day Master's own stem is not labelled with a Ten God. Branches are not directly assigned a Ten God; instead their hidden stems are taken first (see below), then each is related to the Day Master.

Hidden stems and the Five Elements distribution

An earthly branch is composite — it hides one to three heavenly stems, called hidden stems. The first is the main qi, the branch's dominant nature:

  • Zi hides Gui; Mao hides Yi; You hides Xin — only the main qi.
  • Chou hides Ji, Gui, Xin; Yin hides Jia, Bing, Wu; Chen hides Wu, Yi, Gui; Si hides Bing, Geng, Wu; Wei hides Ji, Ding, Yi; Shen hides Geng, Ren, Wu; Xu hides Wu, Xin, Ding.
  • Wu hides Ding, Ji; Hai hides Ren, Jia — two hidden stems.

This tool uses a clear weighting for the Five Elements distribution: each of the four stems counts 10 points; each of the four branches counts 10 points, split among its hidden stems by 60% (main qi), 30% (middle qi) and 10% (residual qi), for a single-stem branch taking the full 10. The total is therefore a fixed 80 points, converted to percentages.

Schools differ on how to weight hidden stems (6/3/1, 7/3, 5/3/2 and others), so the distribution is best used to see the general leaning, not as a precise strength verdict. That is why this tool states its weighting in the notes.

How the Luck Pillars are cast

The Luck Pillars are ten-year steps, with two layers of rules:

  • Direction: a male born in a yang year (year stem Jia, Bing, Wu, Geng, Ren) or a female born in a yin year (Yi, Ding, Ji, Xin, Gui) runs forward; a yang-year female or yin-year male runs backward. So gender only affects direction, not the chart itself.
  • Starting age: counting forward, count to the next solar term; counting backward, count to the previous solar term. The rule is 3 days = 1 year, i.e. 1 day = 4 months, 1 hour ≈ 5 days. The resulting age is the Luck start age, then a new step every ten years.

This tool starts from the month pillar, taking the pillars after it for forward and before it for backward, listing eight steps (eighty years) together with the age range and Gregorian year range.

What true solar time does

The standard time of Taiwan, Hong Kong and mainland China is all based on 120°E. But the sun actually crosses the meridian at your actual longitude, which can differ by over an hour — for example Urumqi (~87.6°E) has its sun about 130 minutes behind the clock.

True solar time conversion has two parts:

  • Longitude difference: for every degree west, the sun crosses the meridian 4 minutes later, so (longitude - 120) x 4 minutes.
  • Equation of time: Earth's elliptical orbit and the tilt of the ecliptic mean the true sun and the mean sun differ by up to about ±16 minutes. This tool uses NOAA's approximation.

The converted true solar time is used only to decide the day and hour pillars (since the hour is a local concept); the year and month term boundaries are a single global instant and are not affected by longitude.

Usage reminders

  • The supported range is 1900 to 2100 CE. The solar-term moments come from a precomputed table using the ShouXing astronomical algorithm, accurate to the minute.
  • This tool always reads your input time as Beijing time (fixed UTC+8), and the solar-term table uses the same basis, consistent with ordinary almanacs.
  • Mainland China observed daylight saving time in the summers of 1986-1991 (clock advanced 1 hour). If you were born between mid-April and mid-September in those years, subtract 1 hour from the clock time on the birth record before entering it, or the hour pillar may shift by one hour.
  • Enter the local clock time. If you only remember "about what time", cast with the default first, then nudge it to see whether the result changes.
  • Leap months and lunar dates need not be entered; this tool reads only the Gregorian date and the solar terms.
  • Bazi belongs to folk culture and self-reflection; it is not scientific prediction. Do not use it as the sole basis for medical, legal, investment or any major decision.

Frequently asked questions

Why is my year pillar different from the lunar new year?
Because the year pillar is bounded by the Beginning of Spring, not the lunar first of the month. The Beginning of Spring is usually around February 3-5; someone born in the lunar first month but before the Beginning of Spring counts the previous year for the year pillar.
Why doesn't the month pillar follow the lunar month?
The month pillar follows the twelve 'terms' (Beginning of Spring, Awakening of Insects, Pure Brightness...), not the lunar first of the month. The gap between terms is about 30 days, close to but starting differently from the lunar month.
Born a bit after 11 pm, which day is the day pillar?
This tool switches the day at 23:00, so late Zi hour belongs to the next day — born after 23:00, the day pillar advances one day. This is the common convention of modern charting software, but traditionally some do not switch; the two give a one-pillar difference.
I don't remember what time I was born at all; can I still chart?
The year, month and day pillars are not affected by the hour; you can cast those three first. The hour pillar varies with the branch, but remembering the rough period (e.g. early morning, noon, late night) narrows it down.
Does gender affect the chart?
It does not affect the four pillars, Ten Gods, Five Elements, etc. Gender only decides whether the Luck Pillars run forward or backward.
How is the Five Elements percentage calculated?
Each of the four stems is 10 points; each of the four branches is 10 points, split among hidden stems by 60/30/10 (a single-stem branch takes 10), total 80 points converted to a percentage. Weighting differs by school, so treat it as a leaning reference.
Why does the Luck start age have decimals?
The Luck start converts the time from birth to the next (or previous) term at '3 days = 1 year', so you get results like '3 years 7 months'. Each Luck step's range follows the same logic.
Do I need to enter true solar time?
If you were near 120°E (e.g. Taipei, Shanghai, Hong Kong) the difference is small and you can leave it off. If you were born well west (e.g. Xinjiang, Sichuan) or right on an hour boundary, enabling it may change the result.
Why do the notes mention subtracting an hour for 1986-1991?
Because mainland China observed DST in those summers, the clock ran 1 hour ahead of Beijing time. This tool, like ordinary almanacs, always uses fixed Beijing time (UTC+8), so those born then must subtract 1 hour from the recorded clock time, or the hour pillar shifts by one hour.
Can this result be used as a basis for decisions?
Not recommended. Bazi belongs to folk culture and self-reflection; it is for reference and entertainment only. Do not use it as the sole basis for medical, legal, investment or any major decision.