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Zodiac sign compatibility
Percentages for love, passion, friendship, home and work — with the reasons behind them. Calculated from the aspect and the ruling planets, not pulled out of thin air.
Fire
Earth
Air
Water
How zodiac compatibility is calculated
The percentages on these pages are not taken from a table and not made up. Here is what every number is built from, so that it can be argued with on the merits.
The aspect is the base
It all starts with the distance between the signs around the zodiac. Zero is a conjunction, one sign apart is a semisextile (30°), two a sextile (60°), three a square (90°), four a trine (120°), five a quincunx (150°), six an opposition (180°).
The aspect sets base values across five scales at once rather than one averaged number. That matters: a square scores high on passion — the tension is the spark — and low on home life, because living together is hard for these people. A single overall number wipes that difference out.
Modality: who gives way
Signs are cardinal, fixed or mutable. One modality shared by both means neither is used to giving way: home life and joint work sag, while passion actually grows on the resistance. Different modalities let the roles split by themselves, without negotiation.
The ruling planet — what geometry cannot give
There is a non-obvious trap here: for sun signs, element and modality are a function of distance. A trine always means one element, a square always one modality. So any formula built from distance, element and modality collapses back into seven numbers and adds nothing.
There is exactly one feature the geometry of the circle does not contain: the ruling planet. Mars makes kin of Aries and Scorpio, who sit in an awkward quincunx. Venus does the same for Taurus and Libra, who sit in a square. Such pairs of planets adjust the base, and every adjustment is printed on the page as its own line under «How the numbers add up».
The overall percentage
The five scales are combined with different weights: love 35 %, friendship 20 %, passion, home and work 15 % each. Love weighs most because that is the question people come to a compatibility page with.
There is no random spread in the calculation. The same pair gives the same numbers today, tomorrow and a year from now — otherwise trust in the section would end on the second check.
Why «Leo and Pisces» equals «Pisces and Leo»
The calculation is symmetric: it looks at the distance between the signs, not at which of the two was named first. Both pages open, because people search both ways, but their content is one and the same.
What a sun sign does not replace
A zodiac sign is only the position of the Sun, one detail of a chart among many. A low percentage is not a verdict on a couple but a description of where they will have to negotiate: a quincunx shares neither element nor tempo, and such a relationship is built deliberately rather than by itself.
If you want more precision, calculate the matrix of a couple — it takes two full birth dates rather than two signs.
Frequently asked
From three terms: the aspect between the signs gives the base across five areas, and the modality and the ruling planets adjust it. Every term is listed on the pair's page under «How the numbers add up».
No. The calculation is deterministic: one pair, the same numbers always. The horoscope changes daily; sign compatibility does not.
No. The percentage says how much built-in friction a pair carries, not whether it will work out. A trine guarantees nothing and a quincunx forbids nothing.
The matrix of a couple, from two dates of birth: it works from full dates rather than the position of the Sun alone.