Free Astrology Compatibility Calculator
Compare two complete birth charts for a free personalized compatibility score and insights into chemistry, emotional connection, communication, and long-term potential.
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Zodiac Compatibility by Sign
Start with your Sun sign, then choose a partner's sign to explore the pairing.
Beyond Sun signs
Your real connection lives in both birth charts
Sun signs describe one layer of a relationship. Birth time and location reveal the Moon, Venus, Mars, rising sign, and the planetary links that make each connection unique.
Calculate our complete synastryThe bigger picture
How Does Astrology Compatibility Work?
Birth Chart Compatibility vs Zodiac Compatibility
Zodiac compatibility usually starts with two Sun signs. Their elements and qualities offer a broad language for describing relationship styles: how someone approaches closeness, change, or independence. Birth chart compatibility goes further by comparing the planetary positions in two individual natal charts. Two people with the same Sun sign can have very different Moon, Venus, and Mercury placements, so their relationships may feel quite different. Use the sign guides as an introduction, then enter both birth profiles above for a comparison specific to the two of you.
What Is Synastry?
Synastry is the astrological practice of comparing two birth charts. Astrologers examine aspects, the angular relationships between one person's planets and the other's, alongside house overlays and contacts to chart angles. A trine may symbolize an easy exchange; a square may describe friction that needs attention. Neither tells the whole story alone. The free synastry score summarizes the comparison, while its emotional, attraction, communication, and long-term dimensions help you explore particular patterns. Read the score as an interpretive starting point, rather than a measured probability that a relationship will succeed.
Moon: Emotional Compatibility
In astrology, the Moon describes emotional needs, familiar habits, and what helps a person feel at home. Moon contacts in synastry invite questions about everyday care: does one person need quiet after an argument while the other wants immediate reassurance? Similar rhythms may feel comforting, while different rhythms can ask for more explicit communication. Consider how each person responds to vulnerability, stress, and affection. Emotional compatibility is useful to explore through those lived examples, instead of assuming that a shared Moon sign guarantees understanding.
Venus & Mars: Love and Attraction
Venus represents affection, pleasure, values, and the ways people give and receive love. Mars brings desire, initiative, and the way someone handles conflict. Comparing their placements and cross-chart aspects can help frame why attraction feels gentle, exciting, or occasionally competitive. Strong chemistry can coexist with different expectations about pace, attention, or personal space. Look at attraction alongside the Moon and Mercury: feeling drawn to someone is one part of a connection, while expressing care and talking through differences are equally relevant to daily life together.
Mercury: Communication
Mercury describes thinking, listening, and the exchange of ideas. In a compatibility reading, Mercury contacts can suggest where conversation feels natural and where people may interpret the same words differently. One person might speak directly and decide quickly; another might need time to reflect or talk through every possibility. These differences become more useful when translated into practical questions. How do you ask for clarification? What helps each of you feel heard? A chart comparison offers prompts for that conversation, while your actual listening habits shape what happens next.
Saturn: Long-Term Compatibility
Saturn is associated with time, responsibility, boundaries, and commitment. Its synastry contacts may symbolize steadiness and a willingness to work through difficulties, but they can also describe pressure, criticism, or unequal expectations. A long-term reading considers these themes alongside affection and emotional support. Ask whether commitments feel mutual, whether responsibilities are shared, and whether both people have room to grow. No single Saturn aspect promises permanence. The value of this part of the chart is in identifying the agreements and recurring lessons that deserve an honest conversation.
Why Birth Time Matters
Birth time and location establish the rising sign, chart angles, and houses. In synastry, house overlays describe which areas of one person's life the other's planets symbolically activate, while angle contacts add another layer to the comparison. The Moon also moves enough during a day that an uncertain time can affect its position and aspects. If you do not know a birth time, select the calculator's unknown-time option. You can still explore an estimated comparison, but treat time-sensitive details cautiously and revisit them if a reliable birth record becomes available.
Want to understand your own placements first? Explore your complete birth chart, then return to compare it with your partner's.
Birth Chart Compatibility FAQ
Can you calculate love compatibility by date of birth?
Yes. Date of birth establishes the planetary positions in each natal chart. Adding an exact birth time and location makes the comparison more precise by including houses, angles, and the rising sign.
What is zodiac compatibility?
Zodiac compatibility compares the qualities, elements, and relationship patterns traditionally associated with two Sun signs. It offers a useful starting point for reflecting on attraction, communication, and shared rhythms.
Can incompatible zodiac signs have a good relationship?
Yes. A challenging Sun-sign pairing does not determine the outcome of a relationship. Communication, maturity, shared values, and the rest of both birth charts add far more context.
Is Sun-sign compatibility the same as synastry?
No. Sun-sign compatibility is a broad comparison. Synastry compares two complete birth charts, including the Moon, Venus, Mars, angles, houses, and planetary aspects.
Which planets matter most for love compatibility?
Astrologers commonly examine the Moon for emotional needs, Venus for affection and values, Mars for desire and conflict, Mercury for communication, and Saturn for commitment and longevity.
How accurate is an astrology compatibility calculator?
The precision of the chart comparison depends on the birth details you enter. Correct birth dates, times, and places help calculate planetary positions, houses, and angles more precisely. The compatibility score is an astrological interpretation of those patterns, not a measured probability of relationship success. Use it to explore emotional needs, attraction, and communication alongside your shared values and lived experience.
Do I need an exact birth time for birth chart compatibility?
An exact birth time is recommended, but you can still use the calculator without it. Select 'I don't know the exact birth time' for either person whose time is unknown, and enter both birth dates and birth places. Your comparison will be estimated: houses, angles, the rising sign, and some Moon details may vary. Add a reliable birth time later for a more precise comparison.
A chart shows the pattern. A conversation helps you use it.
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