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FREE COMPATIBILITY CALCULATOR

Birth Chart Compatibility Calculator

Move beyond Sun signs into calculated synastry across attraction, emotion, communication, friction, and long-term rhythm.

Calculated from real astronomyNot guessed from a date range or generated by AI.
Private by defaultYour birth details never appear in a public URL.
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TWO CHARTS IN RELATIONSHIP

What an astrology compatibility calculator compares

A full-chart compatibility calculator compares the calculated placements and aspects in two natal charts. This technique is called synastry, and it can describe areas of ease, friction, recognition, and difference without predicting the relationship's outcome.

01

How is synastry different from zodiac compatibility?

Zodiac compatibility usually compares two Sun signs. Synastry can compare the Moon, Mercury, Venus, Mars, Saturn, angles, and the aspects one person's planets form to the other's chart.

02

What if one birth time is unknown?

Selyune can still compare supported planetary factors, but it removes unreliable angles, houses, and time-sensitive evidence. The result is labeled as limited rather than padded with invented precision.

03

What does a compatibility score mean?

A score summarizes selected, versioned astrological signals across several dimensions. It is a navigation aid for the evidence shown, not a grade for the people or a probability that the relationship will last.

04

Can astrology predict whether a relationship will work?

No. Astrology cannot predict relationship success, marriage, breakup, loyalty, abuse, or health. Synastry may offer prompts for discussing needs and recurring dynamics, but real behavior, consent, safety, communication, and circumstances matter more than a chart score.

05

How does Selyune calculate compatibility?

Selyune calculates both charts and their cross-chart aspects before producing a score or explanation. AI may explain supplied evidence, but it does not create placements, synastry contacts, or the deterministic score.