Heavenly Stems and Earthly Branches: The 22 Characters Behind Every Saju Chart

Open any Saju chart and you will see eight characters arranged in four columns. They can look like an impenetrable wall of Chinese script, but there are only twenty-two different characters you will ever meet: ten Heavenly Stems (천간, cheongan) and twelve Earthly Branches (지지, jiji). Learn these and the whole chart starts to read like a sentence rather than a code.

This article walks through both sets, explains how they combine into the sixty-cycle that measures years, months, days and hours, and shows why a single branch can carry more than one element.

The ten Heavenly Stems

The stems are the "sky" half of each pillar. Each of the Five Elements appears twice, once in its Yang form and once in its Yin form, always in the same order: Wood, Fire, Earth, Metal, Water. Yang versions tend to be described as outward, direct and expansive; Yin versions as inward, refined and adaptive. Korean readers give each stem a nature image, which is a memorable way to hold their personalities in mind:

• 甲 Gap (Jia), Yang Wood: the tall tree. Upright, principled, growing steadily toward the light.
• 乙 Eul (Yi), Yin Wood: the vine and the flower. Flexible, social, finding a way around obstacles.
• 丙 Byeong (Bing), Yang Fire: the sun. Warm, generous, impossible to ignore.
• 丁 Jeong (Ding), Yin Fire: the candle or lamp. Focused warmth, insight, quiet devotion.
• 戊 Mu (Wu), Yang Earth: the mountain. Steady, protective, slow to move and hard to shake.
• 己 Gi (Ji), Yin Earth: the field. Nurturing, practical, able to grow many things at once.
• 庚 Gyeong (Geng), Yang Metal: the axe or raw ore. Decisive, loyal, built for challenges.
• 辛 Sin (Xin), Yin Metal: the jewel. Precise, elegant, sensitive to quality and fairness.
• 壬 Im (Ren), Yang Water: the ocean or great river. Ambitious, curious, always moving.
• 癸 Gye (Gui), Yin Water: rain and morning dew. Intuitive, gentle, quietly persistent.

The twelve Earthly Branches

The branches are the "ground" half of each pillar. They are the twelve animals of the zodiac, but in Saju they are also markers of season and time of day. Each branch belongs to one element, and the four Earth branches sit at the turning points between seasons:

• 子 Ja, Rat: Water, the depth of winter, 11 pm to 1 am.
• 丑 Chuk, Ox: Earth, late winter, 1 am to 3 am.
• 寅 In, Tiger: Wood, the start of spring, 3 am to 5 am.
• 卯 Myo, Rabbit: Wood, full spring, 5 am to 7 am.
• 辰 Jin, Dragon: Earth, late spring, 7 am to 9 am.
• 巳 Sa, Snake: Fire, the start of summer, 9 am to 11 am.
• 午 O, Horse: Fire, midsummer, 11 am to 1 pm.
• 未 Mi, Goat: Earth, late summer, 1 pm to 3 pm.
• 申 Sin, Monkey: Metal, the start of autumn, 3 pm to 5 pm.
• 酉 Yu, Rooster: Metal, full autumn, 5 pm to 7 pm.
• 戌 Sul, Dog: Earth, late autumn, 7 pm to 9 pm.
• 亥 Hae, Pig: Water, the start of winter, 9 pm to 11 pm.

How stems and branches make the sixty-cycle

Stems and branches advance together, one step at a time: 甲子, 乙丑, 丙寅 and so on. Because there are ten stems and twelve branches, the stems run out first and start again while the branches are still turning, and the two only line up with their starting pair again after sixty steps. That is the sixty-cycle, called yukgap (육갑) in Korean, and it is why people in Korea celebrate a sixtieth birthday, hwangap (환갑), as the moment a life returns to the pillar it began with.

You might expect 10 × 12 = 120 pairs, but only sixty exist. A Yang stem always pairs with a Yang branch and a Yin stem with a Yin branch, so combinations such as 甲丑 never occur. This is a handy check if you ever copy a chart by hand: if the polarities do not match, a character is wrong.

The same cycle runs at four speeds. Years step through it once a year, months once a month, days once a day and hours once every two hours. Your four pillars are simply the four positions the cycle had reached at the moment you were born.

Hidden stems: the elements inside a branch

Branches are richer than stems. Each one is said to contain one to three hidden stems (지장간, jijanggan), the elements stored inside it like seeds in soil. The Rabbit 卯 holds only Wood, but the Ox 丑 holds Earth, Water and Metal, the leftovers of winter and the beginnings of autumn's harvest. The Tiger 寅 carries Wood, with Fire and Earth inside, which is why the start of spring already contains the first warmth of summer.

Hidden stems matter most when a reader judges how strong your Day Master is, or when two charts are compared. A Wood Day Master born on a Goat 未 day, for example, has a little Wood root hidden in that branch even though the branch is Earth. Cosmic Saju's Five Elements bars count the eight visible characters, which is the clearest starting point; many professional readers then add the hidden stems for a finer picture.

Reading a pillar as a picture

Once you know the characters, each pillar becomes an image. 丙午 is the sun at noon in midsummer, Fire upon Fire, bright and intense. 癸亥 is rain falling into the winter sea, Water upon Water, deep and still. 甲申 is a tall tree standing on hard autumn metal, a picture of a strong will meeting a demanding environment.

Readers use these pictures because they are easier to remember than abstract rules, and because they capture the relationship inside the pillar: whether the stem and branch support each other, as Water feeds Wood in 甲子, or test each other, as Metal cuts Wood in 甲申. Try it with your own Day pillar. The image you get is often a surprisingly apt summary of how you carry yourself.