Free Zodiac Compatibility Calculator
Enter two birth dates to see how your zodiac signs interact. Get a harmony score, element compatibility, astrological aspect analysis, and a personalized narrative about your relationship dynamic.
Understanding zodiac compatibility
Zodiac compatibility has been studied for over 2,000 years, and while the popular "which signs match" lists are oversimplified, the underlying framework is real: the geometric relationship between two zodiac signs (called an aspect) creates specific energetic dynamics that influence how two people relate.
The most harmonious aspects are the trine (signs 120 degrees apart, sharing the same element) and the sextile (60 degrees apart, in complementary elements). These create natural flow and understanding. The most challenging aspects are the square (90 degrees apart) and opposition (180 degrees apart), which create tension, but tension is not always negative. Some of the most passionate and growth-oriented relationships are built on squares and oppositions.
Element compatibility provides the foundation. Fire signs (Aries, Leo, Sagittarius) and Air signs (Gemini, Libra, Aquarius) share an active, outward-directed energy, and they energize each other. Earth signs (Taurus, Virgo, Capricorn) and Water signs (Cancer, Scorpio, Pisces) share a receptive, inward-directed energy, and they ground and nourish each other. Cross-group pairings require more conscious effort but can be deeply complementary.
Remember: this calculator uses sun sign compatibility only, the outermost layer. A complete relationship analysis would compare full birth charts, examining Venus-Mars dynamics (attraction and desire), Moon-Moon connections (emotional compatibility), and Saturn contacts (commitment and longevity). Sun signs show the broad dynamic; everything else fills in the nuance.
Beyond sun sign compatibility
Sun sign compatibility is popular because it is simple: you only need two birth dates. But relationships are far more complex than a single zodiac placement. Professional astrologers use synastry charts that overlay two complete natal charts to examine dozens of planetary interactions. The Venus-Mars connection reveals physical attraction and romantic chemistry. Moon-Moon aspects show whether two people feel emotionally safe together. Mercury aspects determine communication compatibility.
Sagelon adds cross-system compatibility on top of this. When two people share complementary Life Path numbers in numerology, harmonious zodiac elements in Western astrology, and balancing BaZi elements in Chinese astrology, the signal is stronger than any single system on its own. We have not seen another platform that runs all three together.
For a complete picture of how your personality systems interact, try the free Convergence Snapshot to see your full numerology, astrology, BaZi, and tarot profile in one unified reading.
Types of astrology compatibility
"Are we compatible?" is never a single question. Different planetary placements govern different parts of a relationship. Here are the layers that matter most.
Sun sign compatibility
The broadest layer. Your sun sign reflects your core identity and ego. When two sun signs share an element or form a harmonious aspect, the relationship feels natural on the surface. This is what our calculator above measures, and it is the best starting point when all you have are two birthdays.
Moon sign compatibility
Your moon sign governs your emotional needs, instincts, and how you process feelings. Two people with compatible moon signs tend to feel safe with each other without having to explain why. Clashing moons can make a relationship feel draining even when everything else clicks. Find yours with our moon sign calculator.
Venus sign compatibility
Venus is the planet of love, attraction, and values. Your Venus sign shapes what you find beautiful, how you express affection, and what you need to feel loved. Venus-Venus compatibility tells you whether two people speak the same love language. Venus-Mars connections reveal physical chemistry. You can find your Venus placement in a full birth chart reading.
Synastry (full birth chart comparison)
Synastry overlays two complete natal charts and examines every planetary connection between them. It is the most comprehensive form of astrology compatibility. A synastry reading reveals not just attraction and harmony, but also growth edges, karmic patterns, and long-term potential. To start, both people need a complete birth chart with accurate birth times.
Compatibility by zodiac sign
Every sign pairs differently with every other sign. Pick yours below to read detailed compatibility guides for all 12 pairings.
Aries
March 21 – April 19
Taurus
April 20 – May 20
Gemini
May 21 – June 20
Cancer
June 21 – July 22
Leo
July 23 – August 22
Virgo
August 23 – September 22
Libra
September 23 – October 22
Scorpio
October 23 – November 21
Sagittarius
November 22 – December 21
Capricorn
December 22 – January 19
Aquarius
January 20 – February 18
Popular compatibility pairs
Some pairings get asked about more than others. These are the ones people search for most, whether out of curiosity or because they are living it.
Learn more about the zodiac signs
Understand each sign's personality, element, and relationship style to get more out of your compatibility results.
Go deeper than sun signs
Sun sign compatibility only scratches the surface. Sagelon's Convergence Snapshot maps your full numerology, Western astrology, Chinese astrology (BaZi), and tarot birth card profile in one reading. When two people both have their Snapshots, the patterns across systems tell a much richer story than any single zodiac comparison can.
Get your profile first. Then have your partner, friend, or collaborator get theirs. The cross-system overlaps are where the real signal lives.
Get your free Convergence Snapshot →Last updated March 2026
Frequently Asked Questions
How accurate is zodiac compatibility?
Sun sign compatibility is a starting point, not the final word. It captures the broad elemental and energetic dynamic between two people based on their zodiac signs. For deeper accuracy, a full synastry chart compares all planetary placements between two birth charts: Moon signs for emotional compatibility, Venus signs for love language, Mars signs for conflict style, and more. Sun sign compatibility gives you the headline; synastry gives you the full story.
What does the harmony score mean?
The harmony score (out of 95) reflects the natural ease between two sun signs based on their element (Fire, Earth, Air, Water), their astrological aspect (trine, sextile, square, opposition, etc.), and their modality (Cardinal, Fixed, Mutable). Higher scores indicate more natural compatibility. Lower scores do not mean the relationship cannot work; they mean it requires more conscious effort and may produce more growth through productive tension.
Can incompatible signs have successful relationships?
Absolutely. Some of the most powerful relationships involve 'challenging' sign combinations. Squares (signs 90 degrees apart) create friction that drives growth. Oppositions (signs 180 degrees apart) create magnetic attraction and complementary strengths. Compatibility is not about avoiding challenge. It is about understanding the dynamic so you can navigate it consciously rather than reactively.
What elements are most compatible?
Signs of the same element naturally understand each other: Fire with Fire, Earth with Earth, Air with Air, Water with Water. The next strongest compatibility is between complementary elements: Fire and Air energize each other, while Earth and Water nurture each other. Cross-group pairings (Fire-Water, Earth-Air) are more challenging but often produce the most dynamic relationships when both people are willing to bridge their differences.
Can you check compatibility by birthday alone?
Yes. Your birthday determines your sun sign, which is enough for a general compatibility reading. Sun sign compatibility captures the core personality dynamic between two people: how your elements interact, what astrological aspect your signs form, and whether your modalities clash or complement. It is the most accessible layer of astrology compatibility and a solid starting point. For a more detailed picture, you would add moon signs (emotional compatibility), Venus signs (love style), and a full birth chart comparison.
What is the difference between sun sign and moon sign compatibility?
Sun sign compatibility describes how two people relate on the surface: personality, ego, life direction. Moon sign compatibility goes deeper. It shows whether two people feel emotionally safe together, how they handle vulnerability, and what they need to feel secure in a relationship. You can have great sun sign compatibility but clashing moons, which often shows up as 'we get along but something feels off.' The reverse is also true. A full compatibility reading looks at both.
What is natal chart compatibility (synastry)?
Synastry is the technical term for comparing two full birth charts. It goes far beyond sun signs. An astrologer looks at how one person's planets aspect the other person's planets: Venus conjunct Mars can mean strong physical attraction, Moon trine Moon suggests emotional harmony, Saturn square Venus might indicate commitment challenges. A synastry reading examines dozens of these connections to build a complete picture of relationship dynamics, timing, and long-term potential.
Does moon sign compatibility matter more than sun sign?
It depends on what you are looking for. Sun sign compatibility is about the big picture: do your personalities mesh? Moon sign compatibility is about the inner life: do your emotional needs align? For long-term relationships, many astrologers consider the moon connection more important because it governs daily emotional reality, not just the surface dynamic. The strongest relationships tend to have harmony in both. You can check your moon sign with our free moon sign calculator.
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