How the number is made.

Most compatibility sites will not tell you where their score comes from, which is usually because it comes from nowhere. Here is ours, in full.

Every pairing is scored on five dimensions — spark, communication, trust, values, and the long run — and each one is a weighted blend of five things: the aspect between the two signs, the identity of the element pair, the identity of the modality pair, whether the two share a polarity, and the relationship between their ruling planets.

That last one matters more than it looks. Element, modality and polarity are all determined by how far apart two signs sit — every trine is same-element, every square is same-modality — so a model built only from those would produce seven answers for seventy-eight pairings, and every trine would read identically. The rulerships are what break the symmetry: Taurus and Libra are both Venus-ruled but sit at an awkward angle; Gemini and Virgo are both Mercury-ruled and sit at a hard one.

Some of the results are deliberately counterintuitive, because the tradition is. A square scores near the top on spark and badly on everything else. An opposition is the most magnetic angle on the wheel and only moderately easy to live in. A pairing can be difficult and extremely compelling at once — most of the interesting ones are.

The score is computed on our own servers in a few milliseconds, and it is deterministic: the same two signs always give the same number, today and next year. A compatibility percentage that drifts between page loads is not measuring anything, and it cannot be shared honestly.

If you add birth details, we compute the actual planetary positions for both charts and the aspects between them, and use those to refine the five dimensions. That is real astronomy, calculated locally from an open-source ephemeris — and it adjusts the reading rather than replacing it, because you came here about two signs.

It is, all of it, for entertainment and self-reflection. It is a good model of a tradition, not a measurement of a relationship. Nobody should leave anybody over a number on a website.