How we calculate compatibility
Most compatibility calculators hand you a percentage and never explain where it came from. We used to do the same, and a precise-looking number like “94%” was the most dishonest thing on this site, because no such measurement exists in either tradition. So we removed every fabricated score. What you see now is an honest band (Harmonious, Workable, Neutral, Demanding, or Combustible) read directly from the real, named relationships the traditions actually define. Here is exactly how it works.
Primary sources
The Chinese side rests on Theodora Lau's The Handbook of Chinese Horoscopes, the most widely cited modern treatment of the tradition and the standard reference for the Triangle of Affinity. The Western side uses classical Hellenistic correspondences (element groupings and modalities) that predate any single author and sit in the public domain. We cite Lau's framework under fair use, for education, and we don't pretend either tradition is science. They are systems of belief with long histories, and we treat them as such.
Reading Chinese pairs
The animals are a folk overlay on the twelve Earthly Branches (地支), and the branches carry a small web of named relationships that the tradition has used for centuries. Our engine computes which of them hold between any two animals. There is no scoring curve to tune, just the relations themselves:
- 六合 Six Harmony and 三合 Trine: natural binding and shared long-term direction. These read as Harmonious.
- 六沖 Clash: direct opposition across the branch wheel. This reads as Combustible.
- 六害 Harm and 刑 Punishment: quiet undermining and grinding conflict. These read as Demanding.
- No classical relation reads as Neutral; and because a single pair can carry more than one relation at once (寅 and 巳, for instance, are both a Harm and a Punishment), a pair that mixes a harmony with friction is honestly stepped down rather than rounded up.
Reading Western pairs
Tropical signs have no branch relations, so here we read the classical element and modality geometry. The twelve signs split across four elements: Fire, Earth, Air, Water. Two signs of the same element share a temperament (Harmonious); the complementary pairings (Fire with Air, Earth with Water) read as Workable; the opposing combinations (Fire with Water, Earth with Air) read as Demanding; and a shared modality between different elements (the classical square) adds friction. Each sign's element, modality, and ruler are shown on its sign page.
Why a band, not a number
Neither tradition produces a percentage, so we don't invent one. A band is a reading aid, not a measurement. A Combustible result doesn't mean a relationship is doomed, and a Harmonious one doesn't guarantee two people will get along. It means the tradition describes an easier or harder starting temperament. The underlying relation is always named on the page, so you can check the reading against the source rather than trust a black box.
How the engine and pages are made
The branch relationships above are classical Chinese-astrology canon, long predating any modern author, and they are computed deterministically by our open calculation engine, the same engine that places the year boundary at 立春 rather than January 1. The prose on each page is written by hand, checked against the source frameworks, and dated; a calculator can name a relation in a millisecond, but explaining what it means takes a person. If you spot an error, tell us and we correct things.
For entertainment and reflection
None of this is fortune-telling. Read every result as traditional belief and a prompt for reflection, never as a prediction or as advice for real decisions. The full disclaimer lives in our Terms.