A four pillars calculator with exact solar terms
This free four pillars calculator draws up a BaZi (八字, “eight characters”) chart: the year, month, day and hour pillars, each a heavenly stem over an earthly branch. It shows the day master — the stem of the day pillar, which BaZi treats as the person — the five-element balance, the hidden stems in each branch, the ten gods, and the ten-year luck pillars.
The month and year boundaries are not taken from a printed table. They come from the solar terms, the moments the Sun reaches every 15° of longitude, computed from a VSOP87 solar model and checked against the Hong Kong Observatory’s published times. That matters for anyone born within a day of a term, such as early February, when the year pillar changes at Lichun rather than at Chinese New Year.
BaZi is a cultural tradition; this page is for tradition and entertainment, not prediction or advice.
How to use the Four Pillars (BaZi) Calculator
- Enter the date and time of birth, or tick Time unknown for a three-pillar chart.
- Choose the birth place and its time zone: daylight saving and historical offsets are applied from your browser’s time-zone data.
- Pick how the hour is read: Clock time, Local mean time (from the longitude) or True solar time (also correcting for the equation of time), and the Zi hour rule for births between 23:00 and midnight.
- Read the four pillars, the day master, the element bars and the luck pillars; choose Luck pillars for male or female, which sets their direction.
- Press Now for the pillars of the present moment, or Copy the chart.
Four Pillars (BaZi) Calculator features
Exact solar terms
Lichun and the eleven other jie terms from a VSOP87 Sun, within about a minute of the Hong Kong Observatory.
All four pillars
Year, month, day and hour with Chinese characters, pinyin, yin/yang and element colours.
Day master and ten gods
Each visible and hidden stem labelled by its relation to the day master.
Five elements
Counts of wood, fire, earth, metal and water in the eight characters, plus the hidden stems.
Luck pillars
Eight ten-year pillars with the starting age from the days to the nearest jie term.
Solar time options
Clock, local mean or true solar time, and both Zi-hour conventions.
How the four pillars are calculated
The year pillar follows the sexagenary cycle, with 1984 as 甲子 (Jia Zi), and changes when the Sun reaches 315°, Lichun, about 4 February. The month pillar changes at each of the twelve jie terms: Lichun opens the 寅 (Tiger) month, Jingzhe (345°) the 卯 month, and so on. Its stem follows the “five tigers” rule: in a Jia or Ji year the Tiger month is 丙寅, in a Yi or Geng year 戊寅, and so on.
The day pillar runs in an unbroken sixty-day cycle, here the Julian day number plus 49, modulo 60. The hour pillar splits the day into twelve two-hour branches starting with 子 at 23:00, with stems by the “five rats” rule. Some schools start the new day at 23:00, others at midnight; both are offered.
Worked example: Mao Zedong, born 26 December 1893 in the 辰 hour, gives 癸巳 year, 甲子 month (after Daxue, 7 December), 丁酉 day and 甲辰 hour — the chart published in Chinese sources, and one of the automatic checks.
| Year stem | Tiger-month stem | Day stem | Zi-hour stem |
|---|---|---|---|
| 甲 Jia or 己 Ji | 丙 Bing | 甲 Jia or 己 Ji | 甲 Jia |
| 乙 Yi or 庚 Geng | 戊 Wu | 乙 Yi or 庚 Geng | 丙 Bing |
| 丙 Bing or 辛 Xin | 庚 Geng | 丙 Bing or 辛 Xin | 戊 Wu |
| 丁 Ding or 壬 Ren | 壬 Ren | 丁 Ding or 壬 Ren | 庚 Geng |
| 戊 Wu or 癸 Gui | 甲 Jia | 戊 Wu or 癸 Gui | 壬 Ren |
Reading the chart
The day master’s element is compared with the others through the producing cycle (wood feeds fire, fire makes earth, earth bears metal, metal carries water, water nourishes wood) and the controlling cycle. The ten gods name those relations — Friend and Rob Wealth for the same element, Eating God and Hurting Officer for what it produces, Wealth for what it controls, Officer and Seven Killings for what controls it, Resource for what produces it. Practitioners weigh season, strength and combinations, which this page leaves to them. For the twelve animals alone see the Chinese zodiac calculator; for a Western chart, the birth chart calculator.
Four Pillars (BaZi) Calculator FAQ
Why is my year animal different from the Chinese zodiac?
BaZi changes the year at Lichun, about 4 February, while the zodiac usually follows Chinese New Year, which moves between 21 January and 20 February.
Should I use true solar time?
Many practitioners do, especially when the time zone is far from the local meridian, as in western China or Spain. The page shows both.
What if I do not know my birth time?
Tick Time unknown: the year, month and day pillars are still exact unless the birth was near a solar term or midnight.
What is the day master?
The heavenly stem of the day pillar. BaZi readings are built around it and its element.
How accurate are the solar terms?
Within about a minute of the Hong Kong Observatory for 2025–2026; only births within minutes of a term are affected.
Can BaZi predict my future?
No. It is a traditional system. This page is for tradition and entertainment, not prediction or advice.