Free calculator
Compare two charts
Calculated from real planetary positions for your exact time and place. Nothing is saved unless you continue to your reading.
Quick answer
The compatibility calculator above compares two people's Sun, Moon, Venus and Mars signs and the elements they fall in. It shows where your styles of identity, emotion, affection and desire naturally match and where they need translating. It is a quick first look, not a verdict. A full synastry and composite comparison adds exact angles, houses and the relationship's own chart.
Key takeaways
- The calculator compares Sun, Moon, Venus and Mars signs for two people, plus the elements those signs belong to.
- Matching or complementary elements suggest ease; mismatched elements suggest areas that need translating.
- A sign comparison misses exact aspects, houses, the rising sign and, above all, how two people actually behave.
- Full synastry and composite charts go much deeper, but no score or chart can predict a relationship.
Sun sign compatibility lists are everywhere, and most of them are too simple to be useful. Two Scorpios are not all the same, and neither are two Geminis. The calculator above goes a step further. It compares four placements for each person, the Sun, Moon, Venus and Mars, along with the elements they fall in.
That makes it a better first look than a Sun sign chart. It is still a first look. This guide explains what the calculator compares, how to read the result, what a quick comparison cannot see, and what a full synastry and composite reading adds.
What does the compatibility calculator need?
It needs each person's birth date, and ideally their birth time and birth city. The date sets the Sun, Venus and Mars, which usually do not change sign within a day. The time pins down the Moon, which changes sign about every 2.5 days. The city lets the calculator apply the right time zone and the daylight saving rules in force where each person was born.
Enter each birth time exactly as written on the birth record, in local clock time. The city handles the conversion. If one of you does not know your time, the result is still useful, but treat the Moon comparison with some caution. Our guide to finding your birth time lists where to look.
What does the calculator compare?
It compares four placements, each describing a different part of how you relate:
| Placement | What it describes | What the comparison shows |
|---|---|---|
| Sun | Core identity and life pace | Whether your basic energy and goals feel familiar or foreign |
| Moon | Emotional needs and what feels safe | Whether you comfort each other easily or need to learn how |
| Venus | Love style, affection, what you value | Whether you give and receive love in similar ways |
| Mars | Desire, drive and how you handle conflict | Whether your pursuit and fighting styles mesh or clash |
The Moon and Venus comparisons usually matter most day to day. Two people can have wildly different Sun signs and still feel at home with each other if their Moons get along. Our guide to Moon sign compatibility explains why emotional needs carry so much weight.
It is also worth comparing one person's Venus sign with the other's Mars sign. Astrologers read that pairing as a classic signal of attraction, because it links one person's style of affection to the other's style of desire.
How are the elements compared?
Each sign belongs to one of four elements: fire (Aries, Leo, Sagittarius), earth (Taurus, Virgo, Capricorn), air (Gemini, Libra, Aquarius) and water (Cancer, Scorpio, Pisces). The calculator checks which elements your placements share.
Astrologers usually read the combinations like this:
- Same element: easy understanding. You process life in a similar way.
- Fire and air: often energizing. Air feeds fire's enthusiasm with ideas.
- Earth and water: often nurturing. Earth gives water shape; water softens earth.
- Fire and water, or air and earth: different operating systems. These pairs can work well, but they need more explaining.
- Fire and earth, or air and water: a mix of spark and friction that tends to teach both people something.
The astrologer Stephen Arroyo wrote at length about the elements as basic temperaments. The useful lesson is that "different" does not mean "wrong". It means you may need to translate. Our full guide to element compatibility goes deeper.
How do you read tricky results?
Most results are straightforward. A few situations need a second look.
What if one of you does not know your birth time?
The Sun, Venus and Mars comparisons are still reliable on almost every day, because those planets rarely change sign within 24 hours. The Moon is the uncertain one. If the Moon changed signs on that person's birth date, read both possible Moon signs and see which one sounds more like them.
What if a planet changed sign on one of your birthdays?
Then the birth time decides which sign applies. This is common near the Sun's sign changes, which shift by a day or so from year to year, so fixed "sign dates" online can mislead people born at the edges. An accurate time and city settle it.
What if every element clashes?
That describes two people with different default styles, not a bad match. Many strong couples have very different charts. The value of the result is that it names the differences early, so you can talk about them instead of taking them personally.
Does it work for friends or family?
Yes. The same four placements describe how any two people relate. The Moon comparison is often the most revealing for friendships and family.
What does a quick comparison miss?
A lot. A sign and element comparison is a summary of styles. It leaves out several things that matter:
- Exact aspects. Signs are 30 degrees wide. Two planets in "compatible" signs might be far apart by degree, and two in "clashing" signs might be very close. Exact angles are where much of the real chemistry shows.
- Houses and the rising sign. Where each person's planets land in the other's chart, and how your rising signs meet, need both birth times.
- The rest of the chart. Saturn, the outer planets and the lunar nodes all shape long-term dynamics.
- Real behavior. How two people talk, fight, apologize and show up matters more than any placement.
That last point is worth stressing. The Gottman Institute describes four communication habits, including criticism and contempt, that it links with relationship strain. None of those appear in a chart. They are choices you can change.
What does full synastry and composite add?
Synastry lays two birth charts side by side and looks at every major angle between one person's planets and the other's, plus which houses each person's planets fall in. It shows the specific points where you light each other up or rub each other the wrong way. Read how synastry works for the full method.
A composite chart blends two charts into one by taking the midpoint of each pair of planets. It describes the relationship itself as its own entity, with its own strengths and pressure points. Our guide to the composite chart explains how to read one.
Together they give a far richer picture than a sign comparison. Venara offers a Compatibility report as an add-on to its paid readings.
Does a compatibility score predict your relationship?
No. If you see a score, a percentage-style number or a label like "high harmony", treat it as a summary of patterns, not a forecast. A high result does not mean a relationship will last. A low result does not mean it will fail or that you should leave.
Astrology is a symbolic tradition, and a well-known controlled test (Carlson 1985) did not find support for its predictive claims. The planetary positions are real astronomy. Their meaning is best used as a mirror for conversation. For more on why no pairing is truly off limits, read are some signs really incompatible.
What should you do with your result?
Use it as a conversation starter. Three concrete steps:
- Talk about the Moon comparison. Ask each other: "What actually makes you feel cared for when you are stressed?" Compare the answers to your Moon signs.
- Look at the mismatched elements as translation work. Pick one difference and agree on one small habit that bridges it.
- Know your own love placements first. Your Venus and Moon describe what you bring to any relationship. You can see your free reveal in about 90 seconds, then compare with your partner when they take theirs.
Frequently asked questions
How does a birth chart compatibility calculator work?
It calculates where the Sun, Moon, Venus and Mars were for each person at birth, then compares the signs and their elements. Signs in the same or complementary elements are read as natural ease. Signs in elements that work differently are read as places where you may need to explain yourselves. It is a quick summary of styles.
Can a compatibility calculator tell if a relationship will work?
No. It can describe how two people's styles of loving, feeling and wanting tend to fit, which can be a useful conversation starter. Whether a relationship works depends on how you communicate, handle conflict, share values and treat each other. Those are choices and habits no chart can measure.
Which planets matter most for compatibility?
Most astrologers look first at the Moon, for emotional needs, and Venus and Mars, for affection and desire. The Sun adds identity and pace. A full reading also looks at the rising sign, the 7th house and exact aspects between the two charts. No single planet decides compatibility on its own.
Do we both need a birth time for the compatibility calculator?
It helps. Sun, Venus and Mars signs are usually clear from the date alone. The Moon changes sign about every 2.5 days, so without a time you may not know it for sure. A full synastry comparison, which uses the rising sign and houses, needs both birth times.
What is the difference between synastry and a composite chart?
Synastry lays two birth charts side by side and looks at the angles between one person's planets and the other's. A composite chart blends the two into one chart by taking the midpoint of each pair of planets, and describes the relationship as its own entity. Many astrologers use both.
Sources
- Stephen Arroyo, Astrology, Psychology and the Four Elements (1975)
- The Gottman Institute: The Four Horsemen
- Carlson, S. (1985). A double-blind test of astrology. Nature, 318, 419-425
- Astronomy Engine (open-source ephemeris library by Don Cross)
About this article
Written and checked by the Venara editorial team against the sources listed and Venara's chart engine. Astrology here is a tool for reflection, not a prediction or professional advice. How we write and check articles.
For entertainment and self-reflection. Not a substitute for professional advice.