BaZi Calculator (Four Pillars of Destiny Birth Chart)

How it works

Year pillar changes at Lichun (Sun at 315°, about February 4): stem = (Y − 4) mod 10, branch = (Y − 4) mod 12 · month branch from the solar terms (jie) every 30° from 315° (Yin month first); month stem = 2 × (year stem mod 5) + 2 + month index · day pillar = (Julian Day Number + 49) mod 60 · hour branch = ⌊(hour + 1) ÷ 2⌋ mod 12; hour stem = 2 × (day stem mod 5) + hour branch

BaZi ("eight characters") describes the moment of birth with four pairs of a heavenly stem and an earthly branch from the 60-day Chinese sexagenary cycle — the year, month, day and hour pillars. The year and month pillars follow the Sun, not the lunar calendar: the year starts at Lichun and each month at a solar term, so the calculator converts your local birth time to Universal Time and computes the Sun's longitude (Meeus). The day pillar comes from the unbroken 60-day cycle (January 1, 2000 was Wu Wu, 戊午), and the hour pillar from the two-hour Chinese double hours. The stem of the day pillar is your "Day Master". BaZi is a traditional Chinese fortune-telling practice offered here for cultural interest and entertainment.

Worked example

Born on May 15, 1990 at 14:30 in China (UTC+8): the Sun had already passed Lichun (February 4, 1990), so the year pillar is 庚午 Geng Wu (Metal Horse); the Sun's longitude of about 54° falls in the Snake month that starts at Lixia, giving 庚午's month pillar 辛巳 Xin Si; the day count gives 庚辰 Geng Chen; and 14:30 is in the Wei double hour (13:00–15:00), 癸未 Gui Wei. The chart reads 庚午 · 辛巳 · 庚辰 · 癸未: Day Master Yang Metal, Metal the strongest element (3 of 8 characters) and no Wood.

Sources: Meeus, Astronomical Algorithms (Willmann-Bell), ch. 25 — Solar coordinates · Encyclopaedia Britannica — Chinese calendar and sexagenary cycle

Frequently asked questions