Zodiac Compatibility Calculator
Enter two birthdays to compare your signs: Sun, Moon, Venus, Mars and Mercury, with a compatibility score and the reason for every point.
Zodiac compatibility compares the signs of two people's planets to see where they fit easily and where they clash. Most sites compare only Sun signs. This calculator works out the Sun, Moon, Mercury, Venus and Mars signs for both birthdays and scores eight pairings, giving more weight to the Sun and Moon. The score is a guide to the astrological picture, not a prediction about any real relationship.
How the score is worked out
For each pairing, the calculator counts how many signs apart the two planets are. Astrologers have read these distances, called sign aspects, in the same way for centuries: signs of the same element sit four apart and get on easily; signs three apart share a mode but clash in element. Each distance earns points out of 4:
| Signs apart | Relationship | Points |
|---|---|---|
| 0 | Same sign | 3 |
| 1 | Neighbouring signs | 1 |
| 2 | Sextile | 3 |
| 3 | Square | 1 |
| 4 | Trine | 4 |
| 5 | Quincunx | 0 |
| 6 | Opposition | 2 |
Each pairing then has a weight, because astrologers treat some contacts as more important in a relationship than others. The final score is the points earned as a percentage of the points possible.
| Pairing | Weight | What it describes |
|---|---|---|
| Sun and Sun | 2 | How your core selves and life directions fit |
| Moon and Moon | 2 | Whether you need the same things to feel safe |
| Your Sun, their Moon | 2 | How your nature meets their emotional needs |
| Your Moon, their Sun | 2 | How their nature meets your emotional needs |
| Your Venus, their Mars | 1.5 | Attraction: what you find appealing and how they pursue |
| Your Mars, their Venus | 1.5 | Attraction: how you pursue and what they find appealing |
| Venus and Venus | 1 | Shared tastes in love, pleasure and affection |
| Mercury and Mercury | 1 | How easily you talk and understand each other |
Scores of 80 and above are described as very harmonious; 65 and above are described as easy-going; 50 and above are described as a mix of ease and friction; 35 and above are described as challenging; anything lower as very challenging.
A worked example
Take two people born on April 12, 1990 and September 3, 1991. The first is Aries Sun, Scorpio Moon, Venus in Pisces and Mars in Aquarius. The second is Virgo Sun, Cancer Moon, Venus in Leo and Mars in Libra. Their Suns are quincunx, five signs apart, worth 0 of 4 points. Across all eight pairings they score 38 out of 100: challenging.
| Pairing | Signs | Relationship | Points |
|---|---|---|---|
| Sun and Sun | Aries – Virgo | Quincunx | 0 of 8 |
| Moon and Moon | Scorpio – Cancer | Trine | 8 of 8 |
| Your Sun, their Moon | Aries – Cancer | Square | 2 of 8 |
| Your Moon, their Sun | Scorpio – Virgo | Sextile | 6 of 8 |
| Your Venus, their Mars | Pisces – Libra | Quincunx | 0 of 6 |
| Your Mars, their Venus | Aquarius – Leo | Opposition | 3 of 6 |
| Venus and Venus | Pisces – Leo | Quincunx | 0 of 4 |
| Mercury and Mercury | Taurus – Leo | Square | 1 of 4 |
What each sign relationship means
Same sign
Both in the same sign: instant recognition and shared instincts, though you can also share the same blind spots.
Neighbouring signs
Signs side by side have little in common in element or style. The pairing can feel unfamiliar and needs effort to understand.
Sextile
Two signs apart, in compatible elements (fire with air, earth with water). Read as friendly, stimulating and easy to build on.
Square
Three signs apart, in the same mode but clashing elements. Read as friction and challenge: lively, but needing compromise.
Trine
Four signs apart, in the same element. The most harmonious link: you understand each other without trying.
Quincunx
Five signs apart, with nothing in common in element or mode. Read as awkward and puzzling, calling for constant adjustment.
Opposition
Directly opposite signs. Read as strong attraction between complementary opposites, with a pull between closeness and conflict.
Sun sign compatibility chart
If you only know the two Sun signs, find the row for one and the column for the other. The number is the Sun-and-Sun score on its own, out of 100. It leaves out the Moon, Venus and Mars, which can change the picture a great deal, so use the calculator above when you have the birthdays.
| Ari | Tau | Gem | Can | Leo | Vir | Lib | Sco | Sag | Cap | Aqu | Pis | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Aries | 75 | 25 | 75 | 25 | 100 | 0 | 50 | 0 | 100 | 25 | 75 | 25 |
| Taurus | 25 | 75 | 25 | 75 | 25 | 100 | 0 | 50 | 0 | 100 | 25 | 75 |
| Gemini | 75 | 25 | 75 | 25 | 75 | 25 | 100 | 0 | 50 | 0 | 100 | 25 |
| Cancer | 25 | 75 | 25 | 75 | 25 | 75 | 25 | 100 | 0 | 50 | 0 | 100 |
| Leo | 100 | 25 | 75 | 25 | 75 | 25 | 75 | 25 | 100 | 0 | 50 | 0 |
| Virgo | 0 | 100 | 25 | 75 | 25 | 75 | 25 | 75 | 25 | 100 | 0 | 50 |
| Libra | 50 | 0 | 100 | 25 | 75 | 25 | 75 | 25 | 75 | 25 | 100 | 0 |
| Scorpio | 0 | 50 | 0 | 100 | 25 | 75 | 25 | 75 | 25 | 75 | 25 | 100 |
| Sagittarius | 100 | 0 | 50 | 0 | 100 | 25 | 75 | 25 | 75 | 25 | 75 | 25 |
| Capricorn | 25 | 100 | 0 | 50 | 0 | 100 | 25 | 75 | 25 | 75 | 25 | 75 |
| Aquarius | 75 | 25 | 100 | 0 | 50 | 0 | 100 | 25 | 75 | 25 | 75 | 25 |
| Pisces | 25 | 75 | 25 | 100 | 0 | 50 | 0 | 100 | 25 | 75 | 25 | 75 |
By element
Every sign belongs to one of four elements: fire (Aries, Leo, Sagittarius), earth (Taurus, Virgo, Capricorn), air (Gemini, Libra, Aquarius) and water (Cancer, Scorpio, Pisces). Astrologers read the elements of the two Suns as the basic tone of a match.
Fire and fire
Two fire signs make an energetic, passionate and competitive match. Life is exciting; the risk is two tempers and nobody backing down.
Fire and earth
Fire wants to move; earth wants to build. The match can be productive if fire learns patience and earth some spontaneity.
Fire and air
Air feeds fire. Read as a lively, encouraging match full of ideas and enthusiasm, though both may avoid the practical details.
Fire and water
Fire and water produce steam: strong attraction and strong reactions. Fire's bluntness can hurt water, and water's moods can dampen fire.
Earth and earth
Two earth signs share practical values, loyalty and a wish for security. The match is stable and productive, if sometimes too cautious.
Earth and air
Earth is practical; air is abstract. Read as a meeting of different worlds that works when each values what the other lacks.
Earth and water
Water nourishes earth. Read as a caring, protective and loyal match, with earth giving stability and water giving feeling.
Air and air
Two air signs connect through ideas, talk and a shared social life. Plenty of mental spark; emotional depth may take longer.
Air and water
Air thinks; water feels. Communication about emotions is the main challenge, and the main gift once it is learned.
Water and water
Two water signs understand each other's feelings intuitively and bond deeply. The risk is moods feeding moods.
Questions people ask
Which zodiac signs are most compatible?
Traditionally, signs of the same element (four signs apart) are the easiest matches: Aries, Leo and Sagittarius with each other, and so on. Signs two apart, fire with air and earth with water, come next. But a whole-chart comparison often tells a different story from the Sun signs alone.
Is compatibility only about Sun signs?
No. Astrologers give at least as much weight to the Moon, which is read as emotional needs, and to Venus and Mars, read as attraction. Two people with clashing Sun signs can have very compatible Moons, which is why this calculator compares all of them.
Do we need our birth times?
Only for the Moon, and only on some birthdays. The Moon changes sign about every two and a half days, so on roughly four birthdays in ten it is in one sign in the morning and another by night. The calculator tells you when that happens. Birth times would also allow rising signs and houses, which belong in a full synastry chart.
What is synastry?
Synastry is the detailed comparison of two full birth charts, including exact planetary aspects, rising signs and houses. This calculator is a simpler sign-level version of the same idea.
Can a low score mean a relationship will fail?
No. The score summarises an astrological reading, nothing more. Plenty of astrologers say challenging contacts make relationships interesting and help both people grow.
Where can I find my own signs?
The sun, moon and rising calculator gives your big three, and the Venus and Mars sign calculators explain those placements in more depth.