BaZi Calculator: Four Pillars of Destiny

Written by Orbitarot · Sources: our own engine, positions checked against NASA JPL Horizons (method); place data GeoNames (CC BY 4.0); interpretations our own · Updated October 17, 2026

The four pillars and the sixty-cycle

Bazi means "eight characters". Each of the four pillars is one Heavenly Stem above one Earthly Branch. There are ten stems (Jia, Yi, Bing, Ding, Wu, Ji, Geng, Xin, Ren, Gui), pairs of yang and yin for Wood, Fire, Earth, Metal and Water, and twelve branches (Zi, Chou, Yin, Mao, Chen, Si, Wu, Wei, Shen, You, Xu, Hai), known in English by the zodiac animals Rat to Pig. Stems and branches combine in a fixed cycle of sixty pairs, the same cycle used for years in the Chinese calendar.

• Year pillar: the pair for your birth year, counted from the start of spring.
• Month pillar: set by the solar term you were born in.
• Day pillar: from an unbroken count of days that has run in 60-day cycles for well over two thousand years. Its stem is your Day Master, the element read as yourself.
• Hour pillar: one of twelve two-hour periods.

Solar terms, not the lunar New Year

The most common error in BaZi comes from the start of the year. The popular Chinese zodiac changes animal at Chinese New Year, a lunar date between 21 January and 20 February. BaZi uses the solar calendar instead: the year pillar changes at Lichun, the start of spring, when the Sun reaches 315 degrees of ecliptic longitude, on or near 4 February. The months change at the twelve major solar terms, about every 30 to 31 days.

Example: Chinese New Year 2023 fell on 22 January, and Lichun on 4 February. Someone born on 28 January 2023 is a Rabbit in the popular zodiac, but their BaZi year pillar is still Ren Yin, Water Tiger, because the solar year had not turned yet. Our calculator finds each solar term from the Sun's computed position, to the minute, so births close to a term are placed correctly.

Hour pillar and local time

The twelve double hours start with Zi, 23:00 to 01:00. Two questions decide the hour pillar for births near a boundary, and practitioners disagree on both:

• Clock time or solar time. Many practitioners convert the clock time to local true solar time, which corrects for your distance from the time zone's central meridian, daylight saving and the time of year. In western China or at the edge of a large time zone, that can move a birth by an hour or more. The calculator shows both and uses solar time by default.
• When the day changes. Some schools start the new day pillar at 23:00 (the start of Zi hour), others at midnight. The calculator lets you choose.

Reading the chart

BaZi readers start with the Day Master and ask whether it is strong or weak in its season, then look at how the other seven characters feed, control or drain it through the five-element cycles (Wood feeds Fire, Fire makes Earth, Earth bears Metal, Metal carries Water, Water feeds Wood). The calculator counts the elements across all eight characters, including the hidden stems inside the branches, so you can see the balance at a glance.

BaZi is a traditional Chinese system, and like Western and Vedic astrology it is symbolic, not predictive science. We do not use it to forecast health, wealth, marriage or anything else.

BaZi and related tools

The solar terms that set your pillars come from the same Sun calculation that places the Sun in the zodiac on the zodiac sign calculator. For a Chinese oracle that asks a question instead of reading a birth moment, try the I Ching. Western and Vedic birth charts are on the birth chart and kundli pages.

In Korea the same four pillars are read as saju (사주), with Korean names for the characters, a time correction of about 30 minutes, lunar birthdays and the luck pillars set out the Korean way: see the Korean saju calculator.

Questions

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