The top halves of your four pillars are the ten heavenly stems, and in Korean saju they do not act alone. Certain stems pair off and combine in a pattern called cheongan hap (천간합) — five fixed pairs, each one joining a yang stem with a yin stem. This guide explains the five combinations, what element each one leans toward, why a combination does not always transform, and what a stem combination tends to describe in a reading. It is a tradition meant for reflection and self-understanding, not prediction — and you can see your own stems free, in plain English, in about a minute.
Each of your four pillars has a heavenly stem on top and an earthly branch below. The ten stems each carry a Five Element and a yin or yang polarity, and saju reads them not as isolated boxes but as positions that can attract and bind with one another. When two specific stems sit together, tradition says they are drawn into a combination (hap) — a quiet pull between the two positions, and, under the right conditions, a lean toward producing a particular element.
None of this is read in isolation. A stem combination is one texture within the whole chart, weighed against your Day Master strength, your element balance and the wider pattern — including how the branches below are behaving.
There are exactly five combining pairs among the ten stems. Each pair joins one yang stem with one yin stem, and each leans toward one of the Five Elements. Notice that the element produced is often not one of the two stems that combine:
| Pair (yang + yin) | Korean / hanja | Leans toward |
|---|---|---|
| Gap + Gi | 갑기합 · 甲己 | Earth (土) |
| Eul + Gyeong | 을경합 · 乙庚 | Metal (金) |
| Byeong + Sin | 병신합 · 丙辛 | Water (水) |
| Jeong + Im | 정임합 · 丁壬 | Wood (木) |
| Mu + Gye | 무계합 · 戊癸 | Fire (火) |
For example, Byeong is a Fire stem and Sin is a Metal stem, yet together they lean toward Water. This is part of why stem combinations are treated as a distinct layer of the chart rather than simple element addition.
This is the part most beginners miss, so it is worth saying plainly: a combination is not the same as a transformation. The presence of a combining pair does not automatically turn both stems into the produced element.
Because the stems sit at the visible top of each pillar, their combinations are often read as the outward, social side of a pattern — attraction, partnership, a meeting of two forces. Where it lands depends on which pillars are involved:
Honesty matters in any reading. A cheongan hap does not predict a marriage, a windfall, or a misfortune. It describes a tendency and a texture — attraction, binding, a possible lean toward an element — within a centuries-old framework for self-reflection. It is not a forecast of events and not advice. Read alone, a single combination tells you very little; read in balance with the whole chart, it adds nuance to a picture meant for understanding yourself, not foretelling the future.
Yes. With four stems on top, more than one combining pair can appear, and a single stem can be pulled by two pairs at once — a situation traditionally read as competition or a divided pull. This is normal and is part of why saju is read as a balance rather than a list of isolated rules.
They use the same idea at different scales. Within one chart, a combination describes an internal pull. Between two people, the same combining rules feed into how their stems and branches interact — which is the heart of gunghap (saju compatibility). The five pairs above are the same building blocks, read across two charts instead of one.
Three of the four stems — year, month and day — come from your date alone, so most stem combinations are already visible without the hour. The hour stem can add or complete one more, refining the picture. For more on this, read the guide to saju and birth time.
Right here. The free Cheonmyeongdang calculator turns your birth date and hour into your eight characters, four heavenly stems and Five Elements distribution in plain English — everything you need to start spotting stem combinations.