Calculating Bazi means converting your birth date and time into the Heavenly Stems (Tian Gan) and Earthly Branches (Di Zhi) system to produce four pillars — year, month, day, and hour. Each pillar consists of one Heavenly Stem and one Earthly Branch, carrying a specific Wu Xing element. This process requires the Wan Nian Li calendar and True Solar Time correction based on your birth location.
Sounds complicated? Don't worry — in this article you'll understand the logic behind Bazi calculation step by step. And if you want instant accurate results, you can use the free Bazi calculator at LumiSaju.
What Is Bazi?
Bazi (八字), also known as Four Pillars of Destiny, is a Chinese metaphysical system that reads a person's energy map based on birth time. It has been used for over 1,000 years and forms the foundation of many Asian divination traditions, including Korean Saju.
If you're new to the basics, read What Is Bazi? first as an introduction.
Basic Components: Heavenly Stems and Earthly Branches
Before calculating, you need to understand two main components:
10 Heavenly Stems (Tian Gan)
Heavenly Stems represent heavenly energy and consist of 10 characters, each associated with one element:
| Stem | Pinyin | Element | Polarity | |------|--------|---------|----------| | 甲 | Jia | Wood | Yang | | 乙 | Yi | Wood | Yin | | 丙 | Bing | Fire | Yang | | 丁 | Ding | Fire | Yin | | 戊 | Wu | Earth | Yang | | 己 | Ji | Earth | Yin | | 庚 | Geng | Metal | Yang | | 辛 | Xin | Metal | Yin | | 壬 | Ren | Water | Yang | | 癸 | Gui | Water | Yin |
12 Earthly Branches (Di Zhi)
Earthly Branches represent earthly energy and are associated with 12 Chinese zodiac animals:
| Branch | Pinyin | Animal | Main Element | |--------|--------|--------|-------------| | 子 | Zi | Rat | Water | | 丑 | Chou | Ox | Earth | | 寅 | Yin | Tiger | Wood | | 卯 | Mao | Rabbit | Wood | | 辰 | Chen | Dragon | Earth | | 巳 | Si | Snake | Fire | | 午 | Wu | Horse | Fire | | 未 | Wei | Goat | Earth | | 申 | Shen | Monkey | Metal | | 酉 | You | Rooster | Metal | | 戌 | Xu | Dog | Earth | | 亥 | Hai | Pig | Water |
Each Bazi pillar consists of one Heavenly Stem on top and one Earthly Branch below — producing a total of 8 characters (hence 八字 / Ba Zi = eight characters).
Step-by-Step Bazi Calculation
Step 1: True Solar Time Correction
This is the step most often ignored but critically important. Your recorded birth time uses standard time zone (e.g., WIB, EST). But Bazi uses True Solar Time — the actual sun time at your birth location.
The difference can reach 30 minutes or more, depending on how far your birth city is from the time zone's reference meridian. This correction can change the hour pillar, and in some cases even the day pillar.
Step 2: Determine the Year Pillar (Nian Zhu)
The year pillar is determined from your birth year according to the Chinese lunar calendar (not the Gregorian calendar). Note that the lunar new year typically falls between late January and mid-February. So if you were born in January, your year pillar might still follow the previous year.
The year's Heavenly Stem follows a 10-year cycle, while the Earthly Branch follows a 12-year cycle (zodiac animals).
Step 3: Determine the Month Pillar (Yue Zhu)
The month pillar is based on the 24 Solar Terms — dividing the solar year into 24 periods. This is not based on the 1st of each calendar month.
The month's Heavenly Stem is derived from the combination of the year's Stem and the lunar month using a special conversion table.
Step 4: Determine the Day Pillar (Ri Zhu)
The day pillar is the most important because its Heavenly Stem becomes the Day Master — the core representation of your personality. Read more about What Is Day Master.
Determining the day pillar requires the Wan Nian Li (Ten Thousand Year Calendar) because the Stem-Branch cycle for days doesn't follow a simple pattern — it must be calculated from a historical reference date.
Step 5: Determine the Hour Pillar (Shi Zhu)
A day is divided into 12 periods (not 24 hours), each spanning 2 hours. The hour's Heavenly Stem is derived from the combination of the day's Stem and the hour's Branch.
| Time (True Solar Time) | Branch | |----------------------|--------| | 23:00 - 01:00 | Zi (Rat) | | 01:00 - 03:00 | Chou (Ox) | | 03:00 - 05:00 | Yin (Tiger) | | 05:00 - 07:00 | Mao (Rabbit) | | 07:00 - 09:00 | Chen (Dragon) | | 09:00 - 11:00 | Si (Snake) | | 11:00 - 13:00 | Wu (Horse) | | 13:00 - 15:00 | Wei (Goat) | | 15:00 - 17:00 | Shen (Monkey) | | 17:00 - 19:00 | You (Rooster) | | 19:00 - 21:00 | Xu (Dog) | | 21:00 - 23:00 | Hai (Pig) |
Why Manual Calculation Is Difficult
Let's be honest — calculating Bazi manually is time-consuming and error-prone. You need:
- An accurate Wan Nian Li calendar
- Stem-Branch conversion tables for each pillar
- True Solar Time correction based on your birth city's coordinates
- Understanding of lunar year and month transitions
One small mistake in the hour pillar can change your entire chart interpretation. That's why even professional practitioners use software for calculations.
After You Get Your Chart, Then What?
Once the four pillars are formed, Bazi analysis begins. You'll examine:
- Element distribution — is your chart dominated by one element or balanced? Learn more in Bazi Five Elements
- Day Master strength — this determines which elements benefit or harm you
- 10 Gods (Shi Shen) — element relationships showing career, relationship, and wealth dynamics
- Luck Pillars (Da Yun) — 10-year fortune cycles showing life phases
You can also use your Bazi chart to check relationship compatibility on the Compatibility page.
Calculate Your Bazi Free at LumiSaju
Instead of calculating manually, you can get a complete Bazi chart in seconds. LumiSaju calculates Bazi, Korean Saju, Nine Star Ki, Numerology, and Western Astrology simultaneously — with automatic True Solar Time correction based on your birth city.
Just enter your birth date, birth time, and birth city. The basic report is free, no account needed.