Compatibility
Find out your compatibility by birth date
👤 First Person
Browse Sign Compatibility
View all 78 sign pairings
Gender-Specific Compatibility
How the dynamic changes depending on who's the man and who's the woman
Gender-specific guides available for all 78 pairings. Visit any pair above to find them.
Want to understand your full compatibility?
What Is Astrology Compatibility (Synastry)?
Astrology compatibility, or synastry, is the art of comparing two birth charts to understand how two people relate. Instead of judging a relationship by Sun signs alone, synastry looks at the connections between every planet in both charts — revealing where you flow together, where sparks fly, and where you'll need a little patience.
How Our Compatibility Calculator Works
Our free compatibility calculator builds a complete birth chart for each person, then measures the cross-aspects between the two — the angles your planets make to your partner's. Those aspects are scored to produce an overall harmony rating, so you can see at a glance how naturally your energies align and which connections shape the relationship most.
What You Need to Compare Two Charts
Enter each person's date of birth, exact time of birth, and city of birth. The dates place every planet in its sign, the times reveal the deeply personal Moon and Rising connections, and the locations anchor both charts correctly. Approximate times still give a useful read, but precise birth times unlock the richest compatibility analysis.
Understanding Your Compatibility Score
Your harmony score summarizes the balance of supportive and challenging aspects between two charts. Supportive aspects like trines and sextiles add ease and attraction, while squares and oppositions add intensity and growth. Curious about a specific pairing? Explore our detailed zodiac sign compatibility guides for all 78 sign combinations.
Compatibility FAQ
What is astrology compatibility?
Astrology compatibility, known as synastry, compares two birth charts to reveal how two people connect. By measuring the angles between one person's planets and the other's, it highlights areas of natural harmony, attraction, friction, and growth in a relationship.
How does the compatibility calculator work?
Our free compatibility calculator builds a full birth chart for each person, then analyzes the cross-aspects between the two charts — for example, how one person's Venus connects to the other's Mars. It scores these connections to produce an overall harmony rating along with the specific aspects driving it.
What information do I need to check compatibility?
For the most accurate synastry reading you need each person's date of birth, exact time of birth, and city of birth. The calculator still works with approximate times, but precise birth times unlock the most detailed picture, including the emotionally important Moon and Rising connections.
Is the compatibility calculator free?
Yes, the CosmyDay compatibility calculator is completely free. You can compare any two birth charts and receive a harmony score and cross-aspect breakdown at no cost.
What are synastry cross-aspects?
Cross-aspects are the angles formed between one person's planets and another person's planets. A Sun-Moon trine can signal easy emotional understanding, while a Venus-Mars connection often points to romantic chemistry. These cross-aspects are the building blocks of relationship astrology.
Do birth times matter for compatibility?
Yes. Birth times set each person's Moon sign, Rising sign, and house placements, which carry much of the emotional and day-to-day dynamic between two people. Compatibility can be estimated without exact times, but accurate times make the synastry reading far more reliable.
Which zodiac signs are most compatible?
Signs that share an element — fire, earth, air, or water — often feel an easy, natural rapport, and complementary elements can spark attraction. That said, real compatibility depends on the whole chart, not Sun signs alone, which is why a full synastry comparison is so valuable.