Heavenly Stems and Earthly Branches

Heavenly stems: the ten upper characters

The heavenly stem is the upper character of a pillar and is taken to represent the energy of heaven. There are ten of them; each pair shares one element, and within a pair one is yang and the other yin. Each comes with the image commonly used for it when it becomes the Day Master (일간).

The stems alternate yang and yin in order, and each two share one element. So once you know a character's position, its yin-yang and element follow at once. The odd-numbered ones (甲·丙·戊·庚·壬) are yang and the even-numbered ones (乙·丁·己·辛·癸) are yin; the 1st and 2nd are wood, the 3rd and 4th fire, the 5th and 6th earth, the 7th and 8th metal, and the 9th and 10th water. The yang and yin of the same element are similar in nature but differ in texture. If 庚 is raw iron before it is worked, 辛 is likened to a finished jewel or a blade's edge.

Earthly branches: the twelve lower characters

The earthly branch is the lower character of a pillar and represents the energy of the earth, the seasons and the hours. The twelve animals we call the zodiac animals (띠) are exactly these branches. Months change at the solar terms, so the months in the table below are approximate.

The hours are not clock time but time based on the sun at the place of birth. For details, see the time adjustment in the article "The Four Pillars".

Yin-yang of the branches: four characters whose order and use differ

The branches also alternate yang and yin in order: 子 is first and so yang, 丑 is second and so yin, and so on. But when the Ten Gods are decided, a branch is read by the stem of its most central energy (the main energy, 정기), so for four characters the yin-yang by order and the yin-yang actually used do not match. Halmeoni also calculates by the main energy.

子 and 午 are yang by order, but their main energy 癸 and 丁 are yin, so they are counted as yin; 巳 and 亥 are yin by order, but their main energy 丙 and 壬 are yang, so they are counted as yang. That is why, for a 庚 Day Master, 子 is not water of the same yang (Eating God, 식신) but yin water (Hurting Officer, 상관). This is why the hour branch 子 in the example chart below comes out as the Hurting Officer. Some readings use the yin-yang by order as it is, so for charts containing these four characters the Ten Gods may come out differently depending on where you look.

Reading the eight characters of the example chart

Taking the example from "What Is Saju (Four Pillars astrology)?", the chart of someone born in Seoul at 00:50 on 25 August 2001, character by character gives the following. The relationship to the Day Master 庚 (the Ten God) is also noted.

Laid out like this, four metal characters (辛·申·庚·申) face three fire characters (巳·丙·丙), with a single water character 子 at the end. The same 申 represents the season of birth when it is the month branch and "the ground under my feet" when it is the day branch. A character's meaning is settled only by reading the character itself together with the position it sits in.

The 60 gapja

Pairing the stems and branches one by one in order gives 60 combinations, starting at 甲子 (gapja) and ending at 癸亥 (gyehae). Yang pairs only with yang and yin only with yin, so there are 60 combinations rather than 120. Year names also come round every 60 years, and this is where the name hwangap (환갑) comes from: the 61st birthday, when the name of the year you were born in returns.

A year's name is easy to work out. Subtract 4 from the Common Era year; the remainder when divided by 10 is the stem's position (0 is 甲, 1 is 乙…), and the remainder when divided by 12 is the branch's position (0 is 子, 1 is 丑…). For 2026, 2022 divided by 10 leaves 2, which is 丙, and divided by 12 leaves 6, which is 午, so it is a 丙午 year; for 2001, 1997 leaves remainders of 7 and 5, giving a 辛巳 year. Note, however, that a saju year runs from that year's Ipchun (start of spring, 입춘) until just before the next year's Ipchun.

Hidden stems (지장간): energy hidden inside a branch

Each branch is taken to hide the energy of between one and three stems. These are called hidden stems (지장간). For example, 寅 (in) holds 戊 (mu), 丙 (byeong) and 甲 (gap), and the most central of them, the main energy (정기), is 甲. Hidden stems show less on the surface, and they are read as traits that appear depending on the situation.

Common misconceptions

• 庚 and 申 are the same character: both are yang metal, but 庚 is the energy of a single stem, while 申 is a branch holding 戊·壬·庚 inside it. Because of the 壬 inside 申, 申 is also linked to water energy.
• The personality of your zodiac animal is your personality: the animals are names attached to make the branches easy to remember. Tendencies are read from all eight characters, centred on the Day Master.
• A branch's element always matches its season: 辰·未·戌·丑 sit at the end of each season, but their element is earth. This is because earth is seen as bridging the change from one season to the next.
• The Ja hour (자시) is the single moment of midnight: the Ja hour is the two hours from 11 pm to 1 am, and it is based on the sun, not the clock. In Seoul, the Ja hour runs from about 23:32 to about 01:32 by the clock.

Frequently asked questions

• Which matters more, the stems or the branches? In Halmeoni's strength calculation, the month branch, which represents the season, is the heaviest at 30 points, and each stem is 10 points. This is because the branches represent the season and the roots.
• Do I need to know the Chinese characters? No. Halmeoni's reading material writes the Korean reading alongside, as in "byeong (丙)", and you can look them up any time in the tables in this article.
• Do the characters relate to each other too? Yes. Among stems we look at combinations and clashes, and among branches at the six combinations, three-way combinations, clashes, punishments, harms and wonjin (원진); these are covered in the article "Combinations, Clashes, Punishments and Harms". In the example chart, 辛 and 丙 form a stem combination, and 巳 and 申 are both a six combination and a punishment.
• Why does it go back to the start after 60? When the 10 stems and 12 branches move forward one step together, they return to 甲子 after the 60th pair, the first point at which 10 and 12 line up together.