Saju Compatibility — a Korean four pillars match from two birth dates
Enter two birth dates and the tool builds both eight-character charts, then compares the day pillars. The rules are the traditional ones, applied exactly — which is not the same as being true. Take it as a bit of fun.
Person A
Please enter a date of birth.
Person B
Please enter a date of birth.
Solar calendar only. If you know a lunar birth date, convert it to the solar date first.
Five element relationship
How the score was built
| Item | Value | Points |
|---|
This score comes from exactly two rules: the element relationship between the two day stems, and whether the two day branches harmonise or clash. It is not evidence about a relationship.
If the copy button does not work, press and hold the text box to copy it manually.
How to use
Not knowing the hour is fine. Choose "Hour unknown" and the day pillar comparison still works, because the score never uses the hour pillar.
Saju compatibility, and exactly how this score is built
Korean saju compatibility, or 궁합 (gunghap), is the practice of comparing two birth charts to see how their elements sit together. It is still consulted around engagements in Korea, and it is one of the parts of Korean culture that visitors are most curious about. This tool builds both charts properly, compares the day pillars using two classical rules, and then shows you the arithmetic instead of hiding it.
That last part is the point. Most compatibility sites hand you a number and a paragraph of flattery. This one prints a breakdown table with every point accounted for, so you can see that a score is a rule being applied, not an insight being revealed.
How to use it
Enter both birth dates using the solar calendar, and the hour of birth if you know it. The hour is genuinely optional here: it fills in the fourth pillar of each chart, but the score never uses it, so choosing "Hour unknown" changes nothing about the result. Press Compare charts and you get both charts, the element relationship drawn as a diagram, and the full score breakdown.
What the four pillars are
Saju means "four pillars". Your birth year, month, day and hour are each written as a pair of characters — one heavenly stem and one earthly branch — drawn from a sixty-unit cycle that has been in use across East Asia for about two thousand years. Eight characters in total, hence the fuller name 사주팔자 (sajupalja), four pillars and eight characters.
Each stem and each branch carries one of five elements: Wood, Fire, Earth, Metal or Water. A reading is fundamentally about how those elements sit together, which ones are abundant, which are missing, and which are pushing against each other.
Why only the day pillar drives the score
In traditional practice the day pillar stands for the person themselves: the day stem is you, and the day branch is your immediate circumstances. That makes it the natural place to start a comparison, and it is where most simplified compatibility methods look.
It is also the honest place to stop. A real reading weighs all eight characters, plus the ten-year luck cycles, plus a great deal of interpretive judgement that varies between practitioners. No calculator reproduces that, and one that pretended to would just be generating text. Two rules applied transparently to the day pillar is a smaller claim, and a truthful one.
Rule one: the element relationship between the day stems
The five elements sit in two cycles. In the generating cycle each element feeds the next. In the controlling cycle each element restrains the one two steps ahead. Your two day stems will always land in one of three relationships.
| Relationship | Cycle | Points |
|---|---|---|
| Generating (상생) | Wood feeds Fire, Fire makes Earth, Earth yields Metal, Metal carries Water, Water grows Wood | +22 |
| Same element (비화) | Both day stems share one element | +12 |
| Controlling (상극) | Wood breaks Earth, Earth blocks Water, Water quenches Fire, Fire melts Metal, Metal cuts Wood | −12 |
Rule two: harmony or clash between the day branches
The twelve earthly branches pair up into six harmony pairs and six clash pairs. These are fixed classical pairings, not something this tool invents, and they are the same tables a Korean reader would use.
| Harmony (육합) +18 | Clash (육충) −14 |
|---|---|
| Rat & Ox | Rat & Horse |
| Tiger & Pig | Ox & Goat |
| Rabbit & Dog | Tiger & Monkey |
| Dragon & Rooster | Rabbit & Rooster |
| Snake & Monkey | Dragon & Dog |
| Horse & Goat | Snake & Pig |
Two identical branches score +6. Any other pairing is neutral and scores nothing.
Putting the score together
score = 50 + stem points + branch points + a small pairing adjustment, capped to the range 12–92
Fifty is neutral. The two rules move it up or down, and a small deterministic adjustment derived from the two charts breaks ties between pairings that would otherwise score identically. It is deterministic on purpose: the same two birth dates always give the same number, and swapping who is A and who is B gives the same number too, because the formula is symmetric.
The cap matters as much as the arithmetic. The score can never reach 0 or 100, because a tool that tells two people they are a perfect match, or a hopeless one, is making a claim it has no business making.
Why the chart is computed rather than looked up
The saju year does not start on January 1, and it does not start at the lunar new year either. It starts at 입춘 (ipchun), the solar term marking the beginning of spring, which falls around February 4 but drifts by roughly a day from year to year. The month pillars change at the eleven other major solar terms in the same way.
Rather than approximate those dates, this tool computes the sun's apparent longitude directly and finds the exact moment it crosses each boundary, then labels the result in Korean standard time. That is why someone born on February 2 gets the previous year's pillar here while a simpler zodiac tool would give them the current year's animal. The precise version is the correct one for saju.
What this cannot tell you
It cannot tell you whether two people should be together. There is no evidence that the timing of a birth predicts anything about a relationship, and this page is not going to pretend otherwise. What the tool does is apply a documented cultural rule set accurately and show its work.
Read it the way you would read a horoscope with a friend: as something interesting to talk about. If a real decision is in front of you, the useful information is what you already know about each other, not two characters out of sixteen.
Frequently asked questions
What is saju?
Saju means the four pillars: your birth year, month, day and hour, each written as a pair of characters from the traditional sixty-year cycle. Eight characters in total, which is why it is also called sajupalja, the four pillars and eight characters. Korean fortune readers use those eight characters the way a Western astrologer uses a birth chart, and it remains a normal part of Korean life around weddings, business openings and new years.
Why does the score only use the day pillar?
Because the day pillar is the one traditional readers treat as representing the person themselves, and because using only it keeps the calculation honest and inspectable. A real reading weighs all eight characters against each other with a great deal of interpretation, which no calculator can reproduce. Rather than invent complexity, this tool applies two well-defined classical rules to the day pillar and shows you exactly how each point was awarded.
Do I need to know the hour I was born?
No. The hour changes the hour pillar, and the score never touches the hour pillar, so you get the same number either way. Choose "Hour unknown" and the tool simply omits that column from each chart. Enter the hour if you know it and you will see the full four pillars, which is worth having if you ever visit a reader.
Why does the tool ask for a solar calendar date?
Because the pillars are calculated from the position of the sun, not from the lunar calendar. If your family records a lunar birth date, convert it to the solar equivalent before entering it. Entering a lunar date directly will produce the wrong chart, usually by about a month, which changes the month pillar and can change the day pillar too.
Why might my year pillar differ from my zodiac animal?
Because the saju year does not begin on January 1 or at the lunar new year. It begins at ipchun, the solar term marking the start of spring, which falls around February 4. This tool computes the exact moment of ipchun from the sun's apparent longitude rather than using a fixed date, so someone born in late January or the first days of February gets the previous year's pillar. That is correct saju practice, and it is why the animal here may not match a casual zodiac calculator.
What does the score actually mean?
It means the two classical rules landed a certain way, and nothing more. Fifty is the neutral starting point. The element relationship between the day stems adds 22, adds 12, or subtracts 12. The relationship between the day branches adds 18, adds 6, or subtracts 14. A small deterministic adjustment keeps identical inputs producing identical output, and the result is capped between 12 and 92 so the tool never claims a perfect or hopeless match. Every one of those numbers is printed in the breakdown table.
Should this influence a real decision?
No. Saju is a centuries-old cultural tradition and it is genuinely interesting, but there is no evidence that birth timing predicts compatibility between two people. Two characters out of sixteen cannot describe a relationship. Enjoy it as a conversation starter, and decide the things that matter on what you actually know about each other.
Related tools
Saju and compatibility readings are cultural tradition and entertainment. They have no scientific basis, they are not evidence about any person or relationship, and they predict nothing. Please make real decisions on real information.