How Is Compatibility Scored? The Full Methodology

How is compatibility scored?

Compatibility is scored with synastry: your birth chart laid over your partner's, aspect by aspect, house by house. A score is a weighted read of how two whole charts interact — not a verdict on the two of you, and not something your Sun signs alone can decide. We built the model to answer a practical question — where does this connection flow, and where will it ask for work? — and to show its reasoning, so you stay the one who decides what it means.

Every score on AstraLink rests on the same foundations, and we would rather over-explain them than have you trust a number you can't see inside. If you want the policy version of all this, it lives in our editorial policy; this page is the how-the-sausage-is-made version for compatibility specifically.

How is astrology compatibility calculated, step by step

1. The chart comes first. We use the tropical zodiac (signs measured from the March equinox, the Western standard) and Placidus houses by default, with whole-sign houses available for readers who prefer them. Planetary positions — Sun, Moon, Venus, Mars, the outer planets and the angles — are computed to ephemeris precision inside the app. A birth chart with an exact time and place is the cleanest input; the more precise the data, the more precise the read.

2. The contacts get weighed. Full synastry in the app looks at the connections astrologers actually watch, and weighs them rather than counting them flat:

• Venus–Mars — attraction, desire and the spark of wanting. How you each give and chase affection.
• Moon–Moon — emotional rhythm. Whether you feel at home with each other or constantly out of sync.
• Sun aspects — identity and purpose: do you amplify who the other is, or quietly compete?
• Saturn contacts — commitment and longevity. Saturn is the difference between a spark and a structure.
• 7th-house overlays — the house of partnership itself: whose planets land in the other's relationship zone.

3. Four lenses, one picture. Those contacts are sorted into love, communication, friction and growth, so a score isn't one flat percentage but a profile. High friction with high growth reads very differently from low friction with low growth — one is a forge, the other is a lull. The model is qualitative and weighted, not a point tally, because a single tight Saturn aspect can outweigh three loose trines.

Synastry vs sun sign compatibility

Sun-sign compatibility ("are Leo and Scorpio compatible?") uses one placement out of dozens. It's a fine starting conversation and genuinely useful shorthand, but it's a single data point. Synastry reads the whole chart against the whole chart — Moon, Venus, Mars, Saturn, the angles and all twelve houses — which is why two Leo–Scorpio couples can feel nothing alike. The quick way to see the gap: your Sun is one of roughly forty moving parts, your big three is only the headline, and your rising sign alone reshuffles every house. That's the entire case for using exact birth data whenever you have it.

What the free browser tools actually do

The calculators on this site are honest previews, not the engine:

• A Sun/Moon lookup from a date only can place your Sun and, roughly, your Moon — but it cannot know your rising sign, because that needs your exact time and place. So the preview shows the two or three most likely rising signs instead of pretending to one.
• The compatibility preview compares Sun and Moon elements only — enough for a feel, not a full synastry. It's the trailer; the app is the film.

Full, time-accurate synastry — the weighted model above, with house overlays and an AI interpretation — lives inside Compatibility and Cosmic Dating, where the dating side matches people by whole-chart fit rather than by a swipe. How matching works walks through that end to end.

What the numbers on sign-pair pages mean

When a page says "Taurus and Cancer: 92%," that number is illustrative. It's built from element and modality fit plus the classic sign-to-sign aspect (same element, sextile, square, opposition) — a tendency across the type, not a measurement of you and one specific person. Your real score depends on placements two sign labels can't see: where your Moons, Venuses, Marses and Saturns actually fall. Read sign-pair numbers as a map of the terrain, and your own chart as the route through it.

Sources, review and the honest bit

Astronomical positions come from ephemeris-grade data; interpretation draws on the Western astrological tradition; and any audience statistic we quote is public research only — for context, the Pew Research Center finds about 27% of US adults believe in astrology, rising to 43% of women aged 18 to 49. Every page is drafted with AI assistance and reviewed by a human astrologer on the editorial team before it ships. For time-sensitive transit windows, we point you to the live calendar in the app rather than guess a date.