Free Compatibility Calculator
Enter two sets of birth details to compare charts. See synastry aspects, compatibility score, and relationship dynamics.
What is synastry?
Synastry is the astrological technique of comparing two natal charts to understand relationship dynamics. By examining how one person's planets aspect the other's, synastry reveals areas of harmony, tension, attraction, and growth in a relationship.
Our calculator computes all major and minor aspects between both charts, generates a composite midpoint chart, and produces an overall compatibility score. Powered by NASA's ANISE toolkit for arc-second precision.
More Free Tools
Frequently Asked Questions
What is synastry in astrology?
Synastry is the comparison of two natal charts to understand relationship dynamics. By examining how one person's planets aspect the other's, synastry reveals areas of natural harmony, creative tension, attraction, and growth potential in any relationship.
How is the compatibility score calculated?
The score weights each synastry aspect by type (conjunction, trine, square, etc.), the planets involved (Sun-Moon contacts weigh more than outer planet aspects), and orb tightness. It also considers composite midpoints. The result is a 0-100 score mapped to compatibility tiers.
Do I need an exact birth time for compatibility?
Planet sign positions and most aspects are accurate without an exact birth time. However, the Moon moves roughly 12 degrees per day, so a precise time gives more accurate Moon aspects, which are important for emotional compatibility. House overlays also require an exact time.