What you get
Six checks. One number. Every reason written out.
Compare ↓Two birth charts
Your two charts
Compatibility score: a number for fun, not a verdict on a relationship.
At least one birth hour is missing, so the hour branches are not compared and that chart has three pillars.
What moved the score
Every check, in order of weight
Four pillars
Your chart and theirs
Five elements
Your balance and theirs
The image shows your two emblems, the score and three reasons. No birth dates.
Full compatibility report
The two of you, written out
- 1 First impression and pullWhat each of you noticed first, and why it held.
- 2 How you talkHow the two of you say things, and what gets lost in between.
- 3 Your emotional rhythmTwo emotional tempos, side by side, and where they meet.
- 4 Where you clash and how to repairThe friction your charts carry, and the repair that tends to work.
- 5 What you give each otherWhat each of you brings the other without trying.
- 6 Your cycles side by side, and 2026Both sets of 10-year cycles on one line, and the year ahead for the pair.
Six chapters, about 2,000 words, written from both charts. It opens with both day master emblems, both pillar charts and an element overlap chart.
Gender only sets the direction of each person's 10-year luck cycles. Leave it blank and the last chapter explains the cycles without listing them.
$9.99 · one-time · written in about a minute
One-time payment · Written in about a minute · A private link you can reopen · Only the two of you inside
One reading, written once, kept at a private link you can reopen. Payment is handled by our payment provider, the merchant of record, which also handles tax, refunds and your receipt; your card details never touch our server. We don't keep the birth dates and times you typed for either person. We do keep the two charts worked out from them (pillars, element balance, ten gods, day master strength, special stars, 10-year luck cycles if you chose genders, the pillar of the year it covers, and sun, moon and rising signs), the score and the kind of relationship you picked, so your report link keeps working. Those chart facts are enough to work out both birth dates. If you chose a gender for either person, it is used only to set the direction of that person's 10-year luck cycles; the gender itself is not saved, but the cycles worked out from it are, and they are enough to work out each person's gender too. The other person's details come from you, so only enter someone who is fine with it. Anyone with your report link can read it. Entertainment only.
Read on
What the six checks measure, and how to read the number.
01
How two charts are compared
This saju compatibility calculator puts two birth charts side by side: yours and one other person's, whether that is a friend, a sibling, a partner or anyone else you are curious about. It reads each chart with Korean saju, the four pillars of year, month, day and hour, and adds the sun and moon signs from Western astrology. Neither birthday is stored: both are used for the comparison and dropped. For an hour after each result, only the score and the lines on a share image are kept in memory.
The comparison runs six checks, each with a fixed weight: the two day masters (30), the two day branches (20), the two hour branches (10), the two sun signs (20), the two moon signs (20), and whether each person's day master supplies the element the other chart has least of (10). Each check comes out as a plus, a zero or a minus, and the list under the score shows every one of them with the pair it compared.
02
Day masters: the generating and controlling cycles
In saju, the day master is the heavenly stem of the day you were born. It stands for you inside your own chart, and it belongs to one of five elements: wood, fire, earth, metal or water. A comparison of two charts starts with the two day masters and how their elements meet.
The elements relate in two circles. In the generating cycle each one feeds the next: wood feeds fire, fire makes earth, earth bears metal, metal carries water and water feeds wood. In the controlling cycle each one keeps another in check: wood holds earth, earth dams water, water puts out fire, fire melts metal and metal cuts wood.
Any two different elements sit next to each other on exactly one of these circles. If one day master generates the other, or both share the same element, the check counts as a plus. If one controls the other, it counts as a minus. A minus here describes a push between two elements, not an outcome. Saju reads that push as pressure, and pressure can also sharpen people.
03
Day branches: six harmonies and six clashes
The earthly branch under your day master is your day branch, one of the twelve zodiac animals. Classical saju calls it the spouse palace and treats it as the part of the chart closest to home. The calculator compares the two day branches with the pairings saju has used for centuries.
The six harmonies are pairs of branches that combine: Rat and Ox, Tiger and Pig, Rabbit and Dog, Dragon and Rooster, Snake and Monkey, Horse and Goat. Two day branches from one of these pairs count as a full plus. The six clashes are branches that face each other across the circle of twelve: Rat and Horse, Ox and Goat, Tiger and Monkey, Rabbit and Rooster, Dragon and Dog, Snake and Pig. A clash counts as a minus.
There is a softer bond as well. The three harmonies group the branches into four trios that each build one element: Monkey, Rat and Dragon for water; Tiger, Horse and Dog for fire; Snake, Rooster and Ox for metal; Pig, Rabbit and Goat for wood. Two different branches from the same trio count as half a plus. Two identical branches, or a pair with none of these links, count as zero.
04
Sun and moon: the Western elements
Western astrology gives every sign one of four elements. Aries, Leo and Sagittarius are fire. Taurus, Virgo and Capricorn are earth. Gemini, Libra and Aquarius are air. Cancer, Scorpio and Pisces are water. The calculator looks at the element of each person's sun sign and moon sign.
Two signs of the same element share a temperament. The pairs fire and air, and earth and water, are friendly: air feeds a flame, and water makes the soil fertile. Any other mix, such as fire with water or air with earth, is read as tense.
The sun sign is about how each of you shows up, so a friendly pair of sun signs gets the biggest plus, the same element a smaller plus and a tense pair a small minus. The moon sign is about the inner, emotional side, so there the same element gets the biggest plus, a friendly pair a smaller one and a tense pair a full minus.
05
Hour branches, missing times and the weakest element
When both birth times are known, the two hour branches are compared the same way as the day branches, with a smaller weight. When either time is missing, that check is left out and the other five share the score. Without a time the chart is read at noon, so the hour pillar stays empty. For someone born close to midnight the day pillar, and with it the day master, can then be off by a day. The moon moves about 13 degrees a day, so a noon moon can also land in the wrong sign on a day when it changes signs.
The last check is balance. Each chart counts how many of its characters belong to each element. If the other person's day master is the element your chart has least of, the calculator adds half a plus, and a full plus when that works both ways.
06
How to read the score
The checks are averaged by weight and set on a scale from 0 to 100. A result of 50 means the pluses and minuses cancel out. Higher means more of the checks lean toward ease, and lower means more of them lean toward friction. Every step is in the list under the score, so you can see exactly which pair moved it.
Treat the score as a number for fun, not a verdict on a relationship. Two people are far more than two birth dates, and saju itself reads a chart as tendencies rather than fixed outcomes. A low number can come from a single clash, and a high one says nothing about how two people actually treat each other.