The short answer
Your Korean Saju chart is built from two repeating cycles: the Ten Heavenly Stems (천간, 天干) and the Twelve Earthly Branches (지지, 地支). When you pair them off in order, they generate the sexagenary cycle, a run of sixty stem-branch combinations that resets and repeats. Every one of your four pillars (year, month, day, hour) is one stem stacked on one branch, so the whole system rests on these two lists and how they combine.
A common first question is why there are sixty combinations and not 120. Ten stems times twelve branches is 120 on paper, but only half the pairings are actually used. Stems and branches each carry a Yin or Yang polarity, and the rule is that a Yang stem only pairs with a Yang branch, and a Yin stem only with a Yin branch. That cuts 120 down to 60. The cycle starts at gapja (甲子, the first stem with the first branch) and ends at gyehae (癸亥, the tenth stem with the twelfth branch), then begins again.
Once you understand the stems and branches, the rest of a Saju reading stops looking like mystery symbols and starts looking like a structured chart. Here is how the pieces fit.
The Ten Heavenly Stems (천간)
The Ten Heavenly Stems are a cycle of ten characters. Each one maps to one of the Five Elements (Wood, Fire, Earth, Metal, Water) in either its Yin or Yang form. That is the whole reason there are exactly ten: five elements times two polarities.
So the stems run as five Yang/Yin pairs:
- Wood: Yang Wood, Yin Wood
- Fire: Yang Fire, Yin Fire
- Earth: Yang Earth, Yin Earth
- Metal: Yang Metal, Yin Metal
- Water: Yang Water, Yin Water
The most important stem in your whole chart is the Heavenly Stem of your day pillar. It is called the Day Master (일주/일간, 日主/日干), and it represents you. Everything else in the chart is read in relation to that one stem.
The Twelve Earthly Branches (지지)
The Twelve Earthly Branches are a cycle of twelve characters, and these are the ones most people already recognize: they are the twelve animals of the zodiac (Rat, Ox, Tiger, Rabbit, Dragon, Snake, Horse, Goat, Monkey, Rooster, Dog, Pig). Historically the twelve branches were tied to the roughly twelve-year orbital cycle of Jupiter, which is why there are twelve of them.
Branches also carry element and polarity associations, and they map to months, seasons, and two-hour blocks of the day. That last point matters for your chart: your hour of birth picks the branch of your hour pillar, which is one reason a Saju reading asks for your birth time and not just the date.
How they combine into the sexagenary cycle
Here is the mechanism, step by step:
- Pair the first stem with the first branch. In Korean that first combination is gapja (甲子).
- Move both cycles forward by one. Second stem, second branch.
- Keep going. Because ten and twelve do not divide evenly, the two cycles drift against each other.
- They line up again only after sixty steps, ending at gyehae (癸亥).
- Then it restarts at gapja.
That sixty-step run is the sexagenary cycle, also called the 60 gapja (60갑자) in Korean. The well-known idea of a "60th birthday" being special (hwangap, 환갑) comes straight from this: at sixty years old, the year pillar returns to the same stem-branch combination you were born under.
How the four pillars use all of this
Your Saju chart has four pillars, and each pillar is one stem on top of one branch:
- Year pillar: family background, ancestry, your roots.
- Month pillar: parents and siblings, environment, often work life.
- Day pillar: the self and the spouse; its stem is the Day Master.
- Hour pillar: children and later-life aspirations.
Because each pillar has two characters and there are four pillars, you end up with eight characters total. That is the same structure the Chinese call Bazi (八字, "eight characters"). Korea reads those eight characters through its own interpretive tradition, but the building blocks on this page are shared by both.
Frequently asked questions
Why are there sixty combinations and not 120?
Yin pairs only with Yin, and Yang only with Yang. Stems and branches each have a polarity, so half of the 10 × 12 = 120 mathematical pairings never occur. That leaves 60.
Which character in my chart is the most important?
The Heavenly Stem of your day pillar, the Day Master. It stands for you, and the rest of the chart is interpreted in relation to it.
Do I need to memorize all the Chinese characters?
No. A modern Saju tool converts your birth date and time into the stems and branches for you and labels them in plain language. You can see your own four pillars laid out, with the Day Master marked, in a free reading at sajuapp.app.
Why does my birth time matter?
The hour of birth sets the Earthly Branch (and therefore the stem) of your hour pillar. Without an accurate time, the hour pillar is missing or wrong, which changes part of the reading.
Try it on your own chart
The fastest way to see the stems and branches in action is to generate your own four pillars and look at which ten-stem and which twelve-branch characters landed in each pillar. Enter your birth date and time and you will get all eight characters, with the Day Master identified, in a free Korean Four Pillars reading at sajuapp.app.
The bottom line
The Ten Heavenly Stems and Twelve Earthly Branches are the alphabet of Saju. Ten stems (five elements, two polarities) and twelve branches (the zodiac animals) pair off, Yang with Yang and Yin with Yin, to make sixty combinations. Stack one stem and one branch for each of your four pillars and you have the eight characters that a reading interprets. Learn these two lists and the rest of the chart becomes readable.
Sources: Sexagenary cycle — Wikipedia; Heavenly Stems — Wikipedia; Earthly Branches — Wikipedia; Four Pillars of Destiny — Wikipedia.
Top comments (0)