Synastry Chart Calculator
Explore the cosmic chemistry between two people. Compare planetary aspects, house overlays, and elemental harmony in your synastry chart.
What Is a Synastry Chart?
Synastry compares two birth charts by overlaying them to reveal relationship dynamics. Unlike a simple compatibility score, synastry shows exactly where and how two people connect — which planets harmonize, where tensions arise, and whose energy activates which areas of the other's life.
The word "synastry" comes from the Greek word meaning "together with stars." It is one of the most powerful tools in astrological relationship analysis because it goes beyond general compatibility to reveal the specific mechanics of how two individuals interact on a soul level.
In a synastry analysis, each person's planets are compared against the other person's planets (aspect synastry) and houses (house overlay synastry). This dual approach reveals both the quality of the interaction (aspects) and the life areas where the interaction manifests (houses).
Key Synastry Aspects
The most important cross-chart aspects reveal the specific dynamics between two people. These planetary connections form the backbone of any synastry analysis:
Sun-Moon Connections
Core identity and emotional bonding — when one person's sun aligns with the other's moon, there is a deep sense of mutual recognition and emotional understanding.
Venus-Mars Aspects
Romantic and physical chemistry — these aspects create the spark of attraction, desire, and the way you express love and passion together.
Mercury Contacts
Communication style — how you think together, share ideas, and understand each other on a mental level. Strong Mercury contacts make conversation effortless.
Saturn Aspects
Commitment and staying power — Saturn connections provide the glue that holds relationships together through difficult times, creating durability and long-term potential.
Pluto Connections
Transformation and depth — Pluto aspects create intense, life-changing connections that transform both people. These bonds are powerful but require conscious navigation.
Jupiter Contacts
Growth and expansion — Jupiter connections bring joy, optimism, and mutual encouragement. These aspects help both people grow and expand their horizons together.
House Overlays
When one person's planets fall into the other's houses, they activate those life areas. This is called "house overlay" and it reveals where in your life the other person has the most impact.
For example, if your partner's Venus is in your 7th house, they naturally embody your ideal partner — the qualities of Venus (love, beauty, harmony) are expressed directly in the area of partnership. If their Moon is in your 4th house, they feel like home — their emotional nature resonates with your deepest need for security and belonging.
House overlays are particularly revealing because they show not just what energy is present, but where it shows up in your life. A person with many of their planets in your 10th house, for instance, will significantly impact your career and public image, while someone with planets in your 5th house will activate your creativity, romance, and joy.