Why Learn to Calculate Your Own Bazi Chart?
In an age of instant digital calculators, you might wonder why anyone would calculate a Bazi chart by hand. The answer: understanding the mechanics behind your Four Pillars gives you a depth of appreciation that no automated tool can replace. When you know how the stems and branches are derived, you understand why your chart looks the way it does β and you become a more informed interpreter of its meaning. Plus, there's something deeply satisfying about working with the same ancient calendar system that Chinese metaphysicians have used for over a millennium.
What You'll Need
- Your birth date and exact birth time (as precise as possible, to the hour)
- A Ten-Thousand Year Calendar (δΈεΉ΄ε) β available in many Bazi reference books or online
- A Heavenly Stem and Earthly Branch lookup table (provided below)
- The 24 Solar Terms calendar for establishing the Month Pillar
Let's walk through each pillar step by step, with a worked example.
Step 1: Determine the Year Pillar
The Year Pillar represents the Heavenly Stem and Earthly Branch of your birth year according to the Chinese solar calendar. Important: the Chinese year does not begin on January 1st or even on Lunar New Year. It begins at the Start of Spring solar term (η«ζ₯, Li Chun), which typically falls around February 4th.
To find your Year Pillar:
- If you were born on or after Feb 4: Use the current Gregorian year's stem-branch assignment.
- If you were born before Feb 4: Use the previous Gregorian year's stem-branch assignment.
The Year Pillar follows the 60-year sexagenary cycle. Here is a shortcut: the Heavenly Stem for any year ending in a given digit is fixed:
| Year ends in | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|
| Stem | Geng | Xin | Ren | Gui | Jia | Yi | Bing | Ding | Wu | Ji |
The Earthly Branch cycles every 12 years in this order: Zi (Rat), Chou (Ox), Yin (Tiger), Mao (Rabbit), Chen (Dragon), Si (Snake), Wu (Horse), Wei (Goat), Shen (Monkey), You (Rooster), Xu (Dog), Hai (Pig).
Example: A person born March 15, 1990. 1990 ends in 0 β Geng Stem. The Rat year was 1984; counting forward: 1984 (Rat), 1985 (Ox), 1986 (Tiger), 1987 (Rabbit), 1988 (Dragon), 1989 (Snake), 1990 (Horse). So Year Pillar = Geng Wu (εΊε) β Yang Metal Horse.
Step 2: Determine the Month Pillar
The Month Pillar is determined by the solar term (θζ°) you were born under, not the Gregorian calendar month. The Chinese solar year is divided into 12 "month" periods, each beginning at a specific solar term:
| Month | Solar Term Start | Approx. Gregorian Date | Earthly Branch |
|---|---|---|---|
| 1 (Tiger) | Start of Spring (η«ζ₯) | Feb 4 | Yin (ε― ) |
| 2 (Rabbit) | Awakening (ζθ°) | Mar 6 | Mao (ε―) |
| 3 (Dragon) | Clear & Bright (ζΈ ζ) | Apr 5 | Chen (θΎ°) |
| 4 (Snake) | Start of Summer (η«ε€) | May 6 | Si (ε·³) |
| 5 (Horse) | Grain in Ear (θη§) | Jun 6 | Wu (ε) |
| 6 (Goat) | Minor Heat (ε°ζ) | Jul 7 | Wei (ζͺ) |
| 7 (Monkey) | Start of Autumn (η«η§) | Aug 8 | Shen (η³) |
| 8 (Rooster) | White Dew (η½ι²) | Sep 8 | You (ι ) |
| 9 (Dog) | Cold Dew (ε―ι²) | Oct 8 | Xu (ζ) |
| 10 (Pig) | Start of Winter (η«ε¬) | Nov 7 | Hai (δΊ₯) |
| 11 (Rat) | Major Snow (倧ιͺ) | Dec 7 | Zi (ε) |
| 12 (Ox) | Minor Cold (ε°ε―) | Jan 6 | Chou (δΈ) |
Once you have the Earthly Branch (based on the solar term), use the Year Stem to determine the Month Stem with the "Five Tigers Chasing the Month" chant:
- Jia or Ji Year β Month 1 Stem = Bing
- Yi or Geng Year β Month 1 Stem = Wu
- Bing or Xin Year β Month 1 Stem = Geng
- Ding or Ren Year β Month 1 Stem = Ren
- Wu or Gui Year β Month 1 Stem = Jia
From Month 1's Stem, count forward sequentially through the 10 Stems to your month.
Example continued: Born March 15 β between Mar 6 (Awakening) and Apr 5 (Clear & Bright) β Month 2, Mao Branch (ε―). Year Stem is Geng β "Yi or Geng Year β Month 1 Stem = Wu." Month 1 = Wu Yin. Month 2 = Ji Mao. So Month Pillar = Ji Mao (ε·±ε―) β Yin Earth Rabbit.
Step 3: Determine the Day Pillar
This is the most calculation-intensive step. The Day Pillar follows a continuous 60-day cycle that has been running uninterrupted for millennia. The standard method uses a formula based on a known reference date. The simplest approach for manual calculation:
- Find the Day Pillar for January 1st of your birth year from a Ten-Thousand Year Calendar reference table.
- Count the number of days from January 1st to your birth date.
- Use modular arithmetic: (Reference Stem number + days) mod 10 for the Stem; (Reference Branch number + days) mod 12 for the Branch.
Example continued: Let's say the Year 1990 Day Pillar reference for Jan 1 is Bing Yin (δΈε― ) β or Day Stem 3, Branch 3 in the cycle. Days from Jan 1 to Mar 15 = 31 (Jan) + 28 (Feb, 1990 not a leap year) + 14 (Mar 1-14) = 73 days. New Stem: (3 + 73) mod 10 = 76 mod 10 = 6 β Ji. New Branch: (3 + 73) mod 12 = 76 mod 12 = 4 β Mao. So Day Pillar = Ji Mao (ε·±ε―) β Yin Earth Rabbit. (Note: the actual Day Pillar for March 15, 1990 requires the precise reference value; this is an illustrative example.)
Step 4: Determine the Hour Pillar
The Hour Pillar uses the Chinese two-hour system (ζΆθΎ°):
| Chinese Hour | Time Range | Earthly Branch |
|---|---|---|
| Zi (ε) | 11:00 PM β 12:59 AM | Zi |
| Chou (δΈ) | 1:00 AM β 2:59 AM | Chou |
| Yin (ε― ) | 3:00 AM β 4:59 AM | Yin |
| Mao (ε―) | 5:00 AM β 6:59 AM | Mao |
| Chen (θΎ°) | 7:00 AM β 8:59 AM | Chen |
| Si (ε·³) | 9:00 AM β 10:59 AM | Si |
| Wu (ε) | 11:00 AM β 12:59 PM | Wu |
| Wei (ζͺ) | 1:00 PM β 2:59 PM | Wei |
| Shen (η³) | 3:00 PM β 4:59 PM | Shen |
| You (ι ) | 5:00 PM β 6:59 PM | You |
| Xu (ζ) | 7:00 PM β 8:59 PM | Xu |
| Hai (δΊ₯) | 9:00 PM β 10:59 PM | Hai |
The Hour Stem is derived from the Day Stem using the "Five Rats Seeking the Hour" method:
- Jia or Ji Day β Hour 1 (Zi) Stem = Jia
- Yi or Geng Day β Hour 1 Stem = Bing
- Bing or Xin Day β Hour 1 Stem = Wu
- Ding or Ren Day β Hour 1 Stem = Geng
- Wu or Gui Day β Hour 1 Stem = Ren
Example continued: Born at 9:30 AM β Si Hour (ε·³). If the Day Stem is Ji β "Jia or Ji Day β Hour 1 Stem = Jia." Hour 1 (Zi) = Jia Zi. Hour 2 (Chou) = Yi Chou. Hour 3 (Yin) = Bing Yin. Hour 4 (Mao) = Ding Mao. Hour 5 (Chen) = Wu Chen. Hour 6 (Si) = Ji Si. So Hour Pillar = Ji Si (ε·±ε·³) β Yin Earth Snake.
The Complete Chart
Our example person born March 15, 1990 at 9:30 AM has:
| Pillar | Heavenly Stem | Earthly Branch | Full Name |
|---|---|---|---|
| Year | Geng (εΊ) | Wu (ε) | Geng Wu |
| Month | Ji (ε·±) | Mao (ε―) | Ji Mao |
| Day | Ji (ε·±) | Mao (ε―) | Ji Mao |
| Hour | Ji (ε·±) | Si (ε·³) | Ji Si |
The Day Master is Ji (Yin Earth). To interpret this chart, you would analyze the Ten Gods that each stem represents relative to Ji Earth, check element balance, and examine the Luck Pillars for timing. Or β you could let our AI handle the heavy lifting.
The Easy Way
Manual calculation is a beautiful skill, but it's error-prone and time-consuming. Our free AI-powered Bazi calculator generates your complete Four Pillars chart, Ten Gods, Luck Pillars, and a detailed interpretation in seconds β with zero math required. Whether you calculate by hand or automate, the real value is in the interpretation that follows.