Saju guide

How Saju compatibility (gunghap) works

Gunghap is the Korean practice of comparing two Saju charts. Here is what a reading looks at, why a clash is not a dealbreaker, and how OtterPrism turns it into a score.

· 4 min read

What gunghap is

Gunghap (궁합) is Saju compatibility: reading two birth charts side by side to see how the people fit together. Traditionally families checked it before a marriage. Today people use it for dating, friendships, coworkers, and, among K-pop fans, for comparing idols and members of a group.

1. The two Day Masters

The starting point is how the two Day Masters relate through the five elements. When one element feeds the other (Wood feeds Fire, Water nourishes Wood), the relationship tends to read as supportive and easy. When one controls the other (Metal cuts Wood), it reads as structure, challenge, or attraction, depending on the rest of the charts.

Five stem pairs are said to combine (천간합, cheonganhap): 甲 Yang Wood with 己 Yin Earth, 乙 Yin Wood with 庚 Yang Metal, 丙 Yang Fire with 辛 Yin Metal, 丁 Yin Fire with 壬 Yang Water, and 戊 Yang Earth with 癸 Yin Water. Day Masters that form one of these pairs are read as having a natural pull toward each other.

2. The day branches

The branch under each Day Master is read as a person's inner life and closest partnership, so the two day branches matter a lot.

  • Six harmonies (육합, yukhap), pairs that bond: Rat and Ox (子丑), Tiger and Pig (寅亥), Rabbit and Dog (卯戌), Dragon and Rooster (辰酉), Snake and Monkey (巳申), Horse and Goat (午未).
  • Three harmonies (삼합, samhap), groups that share a direction and energy: Monkey, Rat, Dragon (申子辰, Water); Pig, Rabbit, Goat (亥卯未, Wood); Tiger, Horse, Dog (寅午戌, Fire); Snake, Rooster, Ox (巳酉丑, Metal).
  • Six clashes (충, chung), opposite branches that push against each other: Rat and Horse (子午), Ox and Goat (丑未), Tiger and Monkey (寅申), Rabbit and Rooster (卯酉), Dragon and Dog (辰戌), Snake and Pig (巳亥).
  • Punishments (형, hyeong): subtler patterns of friction, such as Tiger, Snake, Monkey (寅巳申) and Ox, Dog, Goat (丑戌未).

3. Element balance between the charts

A reading also asks whether one chart supplies what the other is missing. If one person has almost no Water and the other has plenty, the pairing is read as complementary. If both are heavy in the same element, that energy gets amplified, which can feel like instant understanding but also like having no counterweight.

4. The roles they play for each other

Through the Ten Gods, each Day Master plays a role in the other's chart. If one person's element generates the other's, they show up as a Resource: someone who supports and teaches. If one controls the other, they show up as Authority or Wealth: structure on one side, attraction and drive on the other. Two Day Masters of the same element mirror each other as Peers, which can mean close friendship or rivalry.

A clash is not a dealbreaker

Gunghap is about dynamics, not verdicts. A clash describes friction and different rhythms, which can also mean excitement and growth; a harmony describes ease, which can also mean comfort without challenge. The same pair can read differently as partners than as coworkers, because different relationships need different things.

How OtterPrism scores compatibility

OtterPrism turns these rules into four axes, each shown on a 40 to 99 scale:

  • Spark: pull, attraction, and energy between two people.
  • Fit: how well their roles and strengths complement each other.
  • Sync: day-to-day rhythm, pace, and friction.
  • Depth: trust and staying power over time.

See idol pair chemistry →Explore group chemistry →

From axes to one chemistry score

Element support, stem combinations, and branch harmonies raise the axes; clashes, punishments, and shared excess lower them. The overall chemistry score weights the axes by relationship: Spark counts most for dating, Depth for long-term partners, and Fit and Sync for friends, family, and coworkers. Scores of 90 and above are labeled soulmate. The rules are fixed, so the same two charts always get the same score.

See your own Saju

Enter a birth date and OtterPrism builds your four pillars, your Day Master, and how you match with your favorite idols.

Read my chart

FAQ

Is a low compatibility score bad?

No. A lower score usually points to friction, such as a branch clash, which also brings energy and growth. It describes how a relationship moves, not whether it will work.

Do zodiac animals decide compatibility?

Only a little. Animal compatibility uses just the year branches. Full gunghap compares all the pillars, especially the Day Masters and day branches.

Do both people need a birth time?

No. Without birth times the hour pillars are left out, but the Day Masters and day branches, the most important parts for compatibility, are still compared.

Can gunghap be used for friends or coworkers?

Yes. The same chart comparison applies; OtterPrism weights the axes differently for dating, partners, friends, family, and coworkers.

More Saju guides

What is Saju?Saju is the Korean way of reading a birth chart built from four pillars of time. Here is how the chart is made, what each part means, and how people in Korea use it today.Saju vs BaZiSaju and BaZi are the Korean and Chinese names for the same Four Pillars chart. The math is identical; the vocabulary and the way people use it differ.Saju vs Western astrologyWestern astrology reads where the planets were when you were born. Saju reads which cycles of time you were born into. Here is how the two charts line up, and where they part ways.
Saju compatibility (궁합 gunghap) explained