Birth-date compatibility
Birth-date compatibility: how the harmony score is calculated
By Inti Foundation · updated
Birth-year compatibility, in its familiar interpretation, is often reduced to one sentence: harmonious zodiac trines are good, while clashing groups should be avoided. This page takes a different approach. It explains where compatibility calculations come from, which parts are determined by zodiac animals and which are not, and how a harmony score should be read. Inti Soul provides a tool that calculates this score from two birth dates. It runs deterministically—the same input always gives the same result—and deliberately never returns 0% or 100%. This article also explains both limits.
Try it now: How two people match by birth date
Zodiac animals are only one part
Zodiac-animal relationships account for one quarter of the Bazi layer's score, not the entire result.
Four systems run in parallel
Numerology, Bazi, Tử Vi, Astrology—each has its own weight.
No 0%, no 100%
The scale stops at 20 and 98. That is a deliberate decision, not a technical limitation.
What birth-year compatibility means in traditional texts
What popular tradition calls birth-year compatibility mostly concerns the Earthly Branches—the twelve branches corresponding to the twelve zodiac animals of birth years. Three relationships are often mentioned: harmonious trines, with three branches four positions apart, such as Monkey, Rat, and Dragon; the six harmonies, consisting of six paired branches such as Rat and Ox; and clashes, with two branches exactly six positions apart, such as Rat and Horse. Inti Soul uses this same relationship table, but as one piece rather than the entire picture.
- Trines and the six harmonies are recorded as points of resonance, explicitly labeled enduring affinity.
- Two branches six positions apart are recorded as a zodiac clash, accompanied by ‘needs harmonizing’—not ‘should be avoided.’
- Sharing the same zodiac animal, or falling into none of these relationships, is classified as neutral.
Why zodiac animals alone tell too little
The zodiac animal comes from the birth year. That means everyone born in the same year shares a branch, and any conclusion based solely on it speaks about millions of people at once. In Inti Soul, zodiac-animal relationships account for one quarter of the Bazi layer's score, while Bazi is only one of four parallel systems. Altogether, the zodiac-animal component contributes less than one tenth of the total. Two people with clashing zodiac animals can therefore still receive a high overall score if their Five Elements fill each other's gaps and the other layers agree. The reverse is also true: compatibility on paper does not raise the score by itself.
What the harmony score is built from
The tool builds two charts from two birth dates and compares them across multiple systems at once, each with its own weight. Results include an overall score and a five-dimensional map: Soul, Passion, Intellect, Life Values, and Karmic Connection. All scoring is pure arithmetic; no language model is involved.
- Numerology reads both people's Life Paths, Soul Urges, and names—so the name field is real data, not a decorative label.
- Bazi compares Day Masters, complementary Five Elements, and zodiac-animal relationships.
- Tử Vi examines the major star in one person's Life Palace and their Spouse Palace in relation to the other's Life Palace.
- Western Astrology compares aspects between planets, including the Sun and Moon.
- Birth time is optional. Without it, all three chart-based layers—Tử Vi, Astrology, and Bazi—receive reduced weights, most strongly Tử Vi; Numerology remains unchanged. The reading also lowers its confidence level instead of pretending certainty.
Why the scale stops at 20 and 98
The displayed scale is capped at both ends deliberately. Its lower bound is 20 because a number such as four percent harmony, attached to a real relationship, stops being information and becomes a statement that hurts the reader. The upper bound is 98 because one hundred percent harmony is an absolute claim, and Inti Soul does not make absolute claims. Consequently, these scores rank pairs relatively; they do not measure the probability of happiness.
How to read a low score
The reading separates two types of signals: points of resonance and areas needing harmony. A low total means more of the latter—more areas where the two people need explicit conversations than others might—not a verdict. The most useful approach is to turn each low dimension into a specific question. Low Life Values: ask whether the differences concern money, family, or pace of life. Low Intellect: ask how you communicate when you disagree. The answers lie in the conversation, not the number.
What this tool does not do
This is a reflection tool. It does not present the future as fact, conclude whether two people should be together, or replace psychological, medical, legal, or financial advice. Nor can it read the other person's thoughts: all it knows is the two birth dates you enter yourself. That person receives no notification. The tool accepts only pairs in which both people are 18 or older. If a relationship involves control, violence, or safety risks, seek someone you trust and professional support first—no reading can replace that.
See how compatible two birth dates are
Enter both birth dates for an instant harmony score and 5-dimensional map. Free, no account required, and the dates you enter are not saved.
View harmony scoreFor self-understanding and reflection — not a verdict.
Frequently asked questions
Should people with clashing zodiac animals be together?
The reading does not answer that question. A clash is recorded with ‘needs harmonizing,’ and contributes only one quarter of the Bazi layer's score. A pair with clashing zodiac animals can still receive a high overall score through other layers.
How does this page differ from the couple compatibility tool?
The couple compatibility tool scores the two people you enter. This page explains how that score works: where compatibility is calculated from, how much the zodiac animals weigh in the total, and why the scale is capped at 20 and 98.
Can I use it if I do not remember my birth time?
Yes. Birth time is optional. Without it, all three chart-based layers receive reduced weights—Tử Vi most strongly, Astrology moderately, and Bazi slightly—and the reading indicates lower confidence. Only Numerology is unchanged, since it needs just a birth date and name.
Is the other person's birth date saved?
No. The public reading calculates and then forgets; it does not write to the database or compare against other profiles. The sharing card carries only derived numbers, not names or birth dates.