Synastry Basics: How to Read Compatibility Between Two Charts

Synastry is the core technique of relationship astrology: overlay two people's natal charts to see where one's planets fall in the other's chart and what aspects they form — revealing the attraction, fit, and tension between them.

The Most Important Contacts

• Sun–Moon contacts: one person's Sun aspecting the other's Moon is among the most important signs of long-term fit — "your core" and "my emotions" echoing each other.
• Venus–Mars contacts: Venus (love and attraction) aspecting Mars (desire and action) brings romantic and sexual chemistry.
• Ascendant contacts: one person's planet on the other's Rising or Descendant often brings a strong "instant recognition" or "this is the one I've looked for."
• Saturn contacts: bring responsibility, commitment, and testing — stabilizing, but potentially heavy.

House Overlays

Seeing which of the other's houses one's planets fall into tells you which area of their life the relationship mainly activates (the 7th house = marriage-oriented; the 8th = deep entanglement).

Reading Mindset

• Many soft aspects = easy rapport; many hard aspects = tension, not necessarily bad — challenge can bring growth and spark.
• Synastry reads "dynamics and tendencies," not a verdict on "whether you can be together"; the work of a relationship is always the final variable.
• Advanced readers also consult the composite chart (the chart of the relationship itself).

To analyze two charts, use the compatibility tool, or cast each chart first with the free natal chart calculator.

(This is an interpretive framework for relationships — not romantic or psychological advice.)