BaZi Calculator (Four Pillars of Destiny)

BaZi (八字, “eight characters”), also called the Four Pillars of Destiny, writes the moment of birth as four pairs of Chinese characters — one heavenly stem and one earthly branch each for the year, month, day and hour. This calculator builds the chart the way Chinese almanacs do: the year changes at Lichun, the start of spring, and each month at a solar term, not at Chinese New Year or on the 1st. It then shows your Day Master, the ten gods, hidden stems, the balance of the five elements and when your ten-year luck pillars begin.

How to use this tool

1. Enter the birth date and the local clock time (or tick the box if the time is unknown).
2. Choose the birthplace, so the time zone, daylight saving and solar terms are right.
3. Pick the sex (it sets the direction of the luck pillars) and, if you follow a school that uses it, solar time or the early/late Zi hour rule.
4. Read the four pillars, the Day Master and the chart table, then the luck pillars.

Formula

Year = (solar year − 4) mod 60 · Month branch from the Sun’s longitude (寅 from 315°) · Day = (JDN + 49) mod 60 · Hour stem from the day stem

The 60-pair cycle starts at 甲子 (0). Month stems follow from the year stem (甲 and 己 years start at 丙寅), hour stems from the day stem (甲 and 己 days start at 甲子). The Sun’s position uses the VSOP87 series; checked against Astronomy Engine, all solar terms from 1900 to 2100 fall within a minute. Luck pillars run forward for a yang year and a man or a yin year and a woman, otherwise backward; the start age is the number of days to the next jie term (forward) or since the previous one (backward), divided by three.

Example

Born 1 January 2000 at 12:00 in Beijing: Lichun had not yet come, so the year is still 己卯 (Earth Rabbit); the Sun stood between Daxue and Xiaohan, giving the 丙子 month; the day was 戊午, and noon falls in the 戊午 hour. The chart reads 己卯 · 丙子 · 戊午 · 戊午, with 戊 Wù, Yang Earth, as the Day Master.