Compatibility Calculator

(Western Astrology)

About Astrological Compatibility

Astrological assessment of compatibility between two people is known as synastry. There are several different approaches to synastry and not all astrologers agree on the most effective procedure.

The most detailed and sophisticated methods involve making a series of comparisons of the two individual birth charts, or drawing up a composite chart to represent the combination of both persons' astrological tendencies.

While opinions on synastry differ, most astrologers agree that the most important features to consider are each person's positions of the Ascendant, Sun, Moon, and faster-moving planets (Mercury, Venus, Mars, Jupiter and Saturn). This is the approach taken here.

Because the three outermost planets (Uranus, Neptune, Pluto) move so slowly through the zodiac signs, people born within a few years of each other will usually share the same sign. The influence of these three planets on relationships is therefore marginal and they are not included in the compatibility analysis.

If you enjoy this, be sure to check out our Compatibility Calculator (Chinese Astrology).

Get Birth Data

While most people know their Star Sign (the Sun's zodiac location at the time of birth), to get the full benefit from the Psychic Science compatibility calculator, you will also need to know each person's birth signs for the Ascendant, Moon, Mercury, Venus, Mars, Jupiter, and Saturn.

If you don't already have this information, you can get it (free of charge) using the Astrologer calculator shown here, which generates natal charts and astrology reports instantly in your browser.

Enter your birth details and select the desired service (choose "Astrology Report" for the FREE birth chart and interpretation). You do not need to enter your real name and can use initials or an alias if you prefer.

By clicking the Database button, you can store your details in your browser and retrieve them later.

You do not need to sign up to use the free services offered by the Astrologer. However, if you open an Astrologer account, your information will also be stored in the Astrologer's web server. This way, you will be able to retrieve your data on any computer or mobile app.

Note: Some of the other services that are available using the Astrologer require payment. These are indicated by a $ sign. Psychic Science takes no responsibility for these third-party services.

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Explore Your Compatibility

Comparing the zodiac signs for each person's Ascendant and key planets will reveal different areas of your compatibility.

ASCENDANT signs indicate SOCIAL compatibility (how you get on socially).

SUN signs indicate TEMPERAMENT compatibility (how your natural personalities interact).

MOON signs indicate EMOTIONAL compatibility (how you relate emotionally).

MERCURY signs indicate INTELLECTUAL compatibility (how you communicate and share thoughts).

VENUS signs indicate ROMANTIC compatibility (how you relate romantically).

MARS signs indicate PHYSICAL compatibility (how you interact physically or sexually).

JUPITER signs indicate IDEOLOGICAL compatibility (how you react to each other's beliefs, values and opinions).

SATURN signs indicate LONG-TERM compatibility (how your relationship may develop and be sustained over time).

How to Use Our Compatibility Calculator

Simply select the relevant zodiac signs for each person's Ascendant, Sun, Moon, and planets.

If you do not wish to use your real names, you can use initials or an alias - or just leave the Name fields blank.

Each area is given a percentage compatibility score and is graded either GREEN (good), AMBER (fair) or RED (poor).

You will also be shown each person's dominant characteristics in the various areas.

As you enter data, the results will be continually recalculated and updated. You do not need to enter all requested information, but the analysis will be more interesting and useful the more data you can provide.

Astrological Compatibility Calculator

Person A

Person B

Ascendant Sign:
Ascendant Sign:

Sun Sign:
Sun Sign:

Moon Sign:
Moon Sign:

Mercury Sign:
Mercury Sign:

Venus Sign:
Venus Sign:

Mars Sign:
Mars Sign:

Jupiter Sign:
Jupiter Sign:

Saturn Sign:
Saturn Sign:

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Average Compatibility (All Selected)

Social Compatibility (Ascendant)

Temperament Compatibility (Sun)

Emotional Compatibility (Moon)

Intellectual Compatibility (Mercury)

Romantic Compatibility (Venus)

Physical Compatibility (Mars)

Ideological Compatibility (Jupiter)

Long-Term Compatibility (Saturn)

How the compatibility scores are calculated

The scores obtained with this tool are calculated using special algorithms that take into account the relationship (similar and complementary) between the following astrological features in the two charts.

  1. Polarities (Positive vs Negative)
  2. Elements (Fire, Earth, Air and Water)
  3. Qualities (Cardinal, Fixed, Mutable)
  4. Signs (Aries, Taurus, Gemini, etc.)

The significance of each of these factors is also weighted, depending on its relevance to the type of compatibility being assessed (Social, Temperament, Emotional, etc.)

Polarities, Elements and Qualities


Astrological polarities, elements and qualities

In traditional astrology, each zodiac sign is considered either positive or negative, depending on whether its influence is largely active or passive (yang or yin). Polarity alternates through the 12 signs, beginning with Aries (positive) and ending with Pisces (negative).

Positive Signs (Active, Yang, Light) - Aries, Gemini, Leo, Libra, Sagittarius, Aquarius

Negative Signs (Passive, Yin, Dark) - Taurus, Cancer, Virgo, Scorpio, Capricorn, Pisces


Each zodiac sign is also associated with one of the classical four elements (Fire, Earth, Air and Water). Again, these cycle through the zodiac, beginning with Aries (Fire) and ending with Pisces (Water).

Astrological polarities, elements and qualities
Fire Signs (Energy) - Aries, Leo, Sagittarius

Earth Signs (Body) - Taurus, Virgo, Capricorn

Air Signs (Intellect) - Gemini, Libra, Aquarius

Water Signs (Emotions) - Cancer, Scorpio, Pisces

Because each element comprises three signs, the element groupings are known in astrology as the Triplicities.

Fire is traditionally considered to be opposed to Water (e.g., water puts out fire). Similarly, Earth and Air are opposites (e.g., body vs mind).


Another traditional cyclical grouping of zodiac signs is based on how each contributes to the seasonal, developmental, or gestatory process. Three 'qualities' (or modalities) are traditionally recognised - Cardinal, Fixed, and Mutable. Cardinal signs are the creative initiators. Fixed signs provide a stable environment and foster maturation. Mutable signs shake things up and allow transformation to occur.

Cardinal Signs (Beginning, Impulse, Inception) - Aries, Cancer, Libra, Capricorn

Fixed Signs (Middle, Continuation, Stability ) - Taurus, Leo, Scorpio, Aquarius

Mutable Signs (End, Change, Movement) - Gemini, Virgo, Sagittarius, Pisces

Because each quality comprises four signs, these groupings are known in astrology as the Quadruplicities. Relationships between the three qualities are complex, and astrologers can have different opinions about which qualities are compatible.

Caution and Disclaimer

All astrological assessments made using this calculator, including compatibility scores and textual descriptors, are provided for entertainment purposes only. No claim is made concerning the accuracy of these assessments. By using this Compatibility Calculator you agree to accept any and all risks and liabilities that may result from its use.

Note that the calculated compatibility scores are not exact measurements, but rather approximate values. Further insight into the astrological dynamics and interpretation of a compatibility score may be obtained by considering the associated textual descriptors.

Finally, please bear in mind that human relationships are complex and, while it may be interesting and entertaining to explore astrological dimensions, they provide, at best, only a partial perspective. They should not be taken too seriously. Also, don't be surprised if they appear wide of the mark. If they seem inaccurate, they probably are. In these circumstances, it is much better to trust your own judgements about people and relationships.

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