Saju compatibility calculator: Korean gunghap for two charts

What is gunghap, and when do Koreans use it?

Gunghap (궁합, 宮合) is the Korean word for reading two saju charts against each other. The Encyclopedia of Korean Culture defines it as divination at the time of marriage: the saju of the groom and the bride are examined, on the basis of yin-yang and five-element theory, to judge whether the two suit each other as spouses. The same entry names two kinds, an outer gunghap (geot-gunghap, 겉궁합) read from the twelve branches and an inner gunghap (sok-gunghap, 속궁합) read from the five elements.

The traditional setting was the betrothal. According to the encyclopedia, the groom's family sent the bride's family a letter called saju danja (사주단자, 四柱單子), which recorded the groom's birth year, month, day and hour. The bride's family had a diviner read it, and gunghap was checked at that point. If the reading was good, the bride's family sent back a letter that set the wedding date, and with that exchange the marriage was agreed.

The encyclopedia entry, written in 1995, also describes a custom in decline. It says the practice was fading as traditional attitudes changed and industrialization advanced, that some people still decided for or against a marriage because of gunghap, and that gunghap also served as a tactful reason to turn down a proposal.

The simplest form of gunghap compares only the birth-year animals. A 2013 paper by Kim Man-tae in Korean Studies Quarterly describes the folk custom: pairs such as Rat and Ox or Rabbit and Dog are welcomed because their branches form a six harmony, and pairs such as Rat and Sheep or Snake and Dog are avoided because their branches are in wonjin (원진, 怨嗔), a relation read as mutual resentment. The year animal is only one of the eight characters in a chart, as the guide to Korean zodiac color animals explains. This calculator reads all four pillars of both people.

The comparison itself is not tied to marriage. The calculator applies the same rules to any two charts and does not use gender in the comparison. Couples are the traditional use, and the result can be read the same way for friends, relatives or coworkers.

What does this calculator compare?

The calculator first builds both charts by the same rules as the saju calculator on the home page. The year and month pillars change at the solar terms, and the day and hour pillars use true solar time at the birthplace. It then runs six checks with fixed lookup tables. No AI model is involved, so the same two sets of birth details always give the same result.

These are relations that a saju reading ordinarily looks at. The Encyclopedia of Korean Culture describes a reading as centered on the day stem and as examining the combinations and clashes among the stems and branches, the producing and controlling of the five elements, and punishment, break, harm and wonjin.

The day pillars count most. The Day Master (ilgan, 일간, 日干) is the stem of the day pillar and stands for the person. Saju tradition also treats the day pillar as the place of oneself and one's spouse, as Kim Man-tae's paper notes. A stem combination between the two Day Masters is the largest single plus in the score, and a six harmony between the two day branches is the next. A clash between the two day branches is the largest single minus. Day branches that are the same character, or that have none of the listed relations, add nothing. When two day branches fit more than one relation, the calculator takes the first in this order: six harmony, three harmony, clash, wonjin, punishment.

Check 3 covers every other pair of branches between the two charts. A pair that involves a day branch counts most, a pair that involves a month branch comes next, and pairs among year and hour branches count least. The calculator also looks for a three harmony, a directional combination or a three-branch punishment that is complete only when the branches of both charts are pooled, and for two branches of a three harmony held one in each chart. A group that one chart already holds on its own is not counted. The pair total and the group total are each capped.

Check 4 counts the characters of each chart by element: eight characters, or six without an hour pillar. A person's scarcest element is the one with the lowest count, and a tie goes to the first in the order Wood, Fire, Earth, Metal, Water. The more characters of that element the other chart holds, the more the check adds, up to a limit. It is counted in both directions.

Check 5 uses Cheoneul Gwiin (천을귀인, 天乙貴人), the best known of the noble stars. Every Day Master has two Cheoneul Gwiin branches. The check asks whether any branch in one chart is one of the two that belong to the other person's Day Master, and it asks this in each direction. The reason line for it appears only when the answer is yes both ways.

Which stems and branches combine or clash?

The tables in this section are the classical lookups behind checks 1 to 3. San Ming Tong Hui (三命通會), a manual of the four pillars compiled by Wan Minying in Ming China in the mid-16th century, sets out the stem combinations, the six harmonies and the clashes in its second volume.

The five stem combinations (cheonganhap) pair the ten Heavenly Stems.

In every stem combination a yang stem meets the yin stem of the element it controls. San Ming Tong Hui explains a combination as harmony between yin and yang and compares it to a man and a woman joining as husband and wife. The last column is the element each pair is traditionally said to turn into. The compatibility check asks only whether the two Day Masters make one of these pairs. It does not change an element in either chart.

The six harmonies (yukhap, 육합, 六合) pair the twelve Earthly Branches.

The six clashes (chung, 충, 沖) pair each Earthly Branch with the one directly opposite it on the circle of twelve. San Ming Tong Hui counts it as the seventh branch from one's own.

A clash is not read as purely negative. Kim Man-tae's paper makes the point that a clash does not only do harm, just as a combination does not only do good. The reason line of this calculator words a day-branch clash in the same spirit: "strong pull with easy friction".

Checks 2 and 3 also use the branch relations in the next table.

In check 2, two day branches from the same three-harmony group count as a three harmony. In checks 2 and 3, any two branches from the same punishment group count as a punishment, and so do 子 and 卯.

One pair of branches can hold more than one relation. 寅 and 亥 are a six harmony and a break at once, and check 3 counts both. Check 3 also counts the same branch appearing in both charts as a slight plus.

How do I read the 50–100 score and the reasons?

The number next to "Gunghap score" is a whole number from 50 to 100. The calculator adds up the six checks and places the total on a curve that starts at 50, so the number is not a percentage and no pair scores below 50. Swapping Person A and Person B gives the same score. The label next to the number follows this table.

Under the score, two lines name the role each person plays for the other. The role comes from the elements of the two Day Masters alone, so the two lines can differ.

Producing and controlling follow the two cycles of five-element theory. The Encyclopedia of Korean Culture gives both cycles in its entry on the theory, and check 6 uses the same table.

The list under "Why this score" holds up to three reasons: the ones that moved the score most, whether up or down. When the score is on the low side, the list always includes a reason that lowered it, if there is one. Smaller items are counted without being listed.

In the example above, the score is 66, "Workable". Person A, born March 15, 1995, has the Day Master 乙, Yin Wood. Person B, born November 2, 1993, has the Day Master 丁, Yin Fire. Wood produces Fire, so the two lines read "To Person A, Person B is: My Person" and "To Person B, Person A is: Benefactor". 乙 and 丁 are not a stem combination, so check 1 adds nothing. The three reasons trace back to the two pillar tables as follows.

The example also holds items that are counted without being listed. Wood producing Fire between the two Day Masters adds a little. A clash between Person A's month branch 卯 and Person B's year branch 酉 takes a little off. Person A's year branch 亥 is one of the two Cheoneul Gwiin branches of Person B's Day Master 丁, which adds a plus in one direction only.

What are the limits of a saju compatibility score?

A gunghap score compares the structure of two charts. It knows nothing about how two people treat each other, what they have been through or what they choose to do. It is not a verdict on whether a relationship should begin, continue or end, and the note under every result says so.

The lookup tables are classical, but the weights are this site's own. Which relations to count, and how much each one matters, are choices made for this calculator. Another practitioner or another calculator can weigh the same harmonies and clashes differently and reach a different number from the same two charts.

The result depends on the birth times. The hour pillar changes every two hours of true solar time and the day pillar turns over at 23:00, so a birth time that is a few minutes off near a boundary can change a day branch, and with it the largest items in the score. If you tick "Birth time unknown" for one person, that chart has no hour pillar and the comparison uses its year, month and day pillars only. The About and method page lists every calculation rule.

The comparison does not read everything in a chart. It leaves out the ten gods within each chart, Day Master strength and the 10-year luck cycles (daeun). To see those, run each set of birth details through the saju calculator on its own and follow the guide to reading a saju chart.

Saju is a traditional practice, and this site does not claim that the score predicts how a relationship will go. The Encyclopedia of Korean Culture reports the prevailing view on gunghap itself: now that couples can get to know each other openly before marriage, people are expected to feel less and less need for it.