Synastry and Zodiac Compatibility

What is synastry, and how does zodiac compatibility work?

Synastry means setting two people’s birth charts side by side, or laying one over the other, to read how one person’s planets touch the other’s planets and houses; zodiac compatibility is its simplest form, comparing only the elements of the two people’s signs. Neither decides the fate of a relationship. They show where two people meet easily, where they strain each other and where they can grow together.

Compatibility rests on the elements. The twelve signs fall into four elements, and the elements relate to each other in different ways:

Element	Signs	Meets easily with	Strains with
Fire	Aries, Leo, Sagittarius	air (feeds fire), fire	water, earth
Earth	Taurus, Virgo, Capricorn	water (feeds earth), earth	fire, air
Air	Gemini, Libra, Aquarius	fire, air	water, earth
Water	Cancer, Scorpio, Pisces	earth, water	fire, air

The table is a starting point. A compatibility reading based on Sun signs alone compares a very small part of each chart. Synastry also brings in the Moon, the rising sign, Venus, Mars and the aspects between the planets. Two people’s Sun signs can look “incompatible” while their Moons understand each other very well.

The contacts most often read in synastry are: Sun and Moon (one touches the other’s core, the other one’s need), Venus and Mars (attraction and passion), Moon and Moon (emotional rhythm), contacts with the rising sign (first attraction and everyday fit) and Saturn contacts (commitment, responsibility and sometimes weight). These are the most visible traces of how two charts touch.

Alongside synastry there is the composite chart: a single chart drawn from the midpoints of two people’s planets, which describes the relationship itself as a “third entity” separate from the two people. Synastry shows how two people touch each other; the composite shows what they become together. Synastry is enough to start with.

How to compare two charts in seven steps

1. Write both people’s big three side by side

Start by writing both people’s Sun, Moon and rising signs next to each other. These six signs give the basic rhythm of the relationship: the Suns show how identities meet, the Moons emotional needs, the rising signs everyday approaches. Begin by knowing your own chart well; it is hard to see how your need meets someone else’s without knowing your own.

2. Compare the elements

Compare each pair through the elements: Sun with Sun, Moon with Moon, rising with rising. Same or nourishing elements show flow; straining elements show the areas that need effort. If one person’s Sun and the other’s Moon share an element, one can meet the other’s need easily.

3. Read the Moons separately

The two Moon signs are the compatibility felt most in daily life together: what does each need when tired or hurt, and how does the other respond? Someone with the Moon in Taurus wants steadiness and comfort, while someone with the Moon in Sagittarius wants room to roam. Knowing that difference prevents a lot of hurt.

4. Look at Venus and Mars

Venus describes how you give love and what you value, Mars how you show desire and passion. When one person’s Venus and the other’s Mars share or nourish an element, attraction is strong. When both Venuses sit in similar elements, the two show love in similar ways. In tarot, the card of relationships and choices, the Lovers, is traditionally paired with Gemini and stands as a symbol of that meeting.

5. Look at the aspects between the charts

Laying two charts over each other creates aspects between one person’s planets and the other’s. A conjunction describes a strong bond, trines and sextiles an easy flow, a square tension and growth, an opposition attraction and a search for balance. Hard aspects do not mean a bad relationship; they show where two people change each other most. Saturn contacts need extra care: they can bring commitment and steadiness, but sometimes leave one partner feeling limited.

6. Look at the house overlays

If birth times are known, see which of the other person’s houses each person’s planets fall into. If one person’s Sun lands in the other’s seventh house, they light up the area of partnership; if it lands in the fourth, they bring a feeling of home and family.

7. Gather it into one sentence

Finally, sum up the comparison in one sentence: “Our identities get along easily, but our emotional rhythms differ; we need to learn each other’s needs.” Make it a work area, not a verdict, and add a “what we do well” sentence beside it; knowing what flows easily strengthens a relationship as much as knowing the hard parts.

Example: a short comparison of two charts

Person one: Sun in Libra, Moon in Cancer, Leo rising. Person two: Sun in Aquarius, Moon in Aries, Sagittarius rising.

The Suns. Both air signs: conversation, swapping ideas and social life flow easily here. They talk a lot and laugh a lot together.

The Moons. A Cancer Moon and an Aries Moon sit in different elements, water and fire: when hurt, person one wants closeness and comfort, person two flares up, says it straight out and then needs some room to cool down. This is the relationship’s most sensitive point.

The rising signs. Leo and Sagittarius, two fire signs: from outside, an energetic, warm, generous couple. The first attraction most likely came from this fire.

Venus and Mars. Say person one’s Venus is in Virgo and person two’s Mars in Capricorn: both earth. The way one shows love and the way the other pursues what they want speak the same language; this couple shows love best through practical help and keeping their word.

One sentence. “Our minds and energy get on very well, but when we’re hurt we want different things: one wants closeness, the other space.” The comparison does not say whether the relationship will last or end; it shows where the couple needs to put in the most work.

The step. Next time there is a hurt, let person one say the need for closeness out loud, and person two say “I need a bit of space, but I’m not leaving.” Naming different needs is the first step to making peace between the Moons.

Common misconceptions about compatibility

• Looking only at Sun signs. The Sun sign is one part of the chart. Talking about compatibility without comparing the Moon, rising, Venus and Mars leaves most of the picture out.
• Believing “incompatible” signs can’t be together. Straining elements and aspects also bring strong attraction and mutual growth.
• Treating compatibility as a guarantee. Even the most compatible charts need communication, effort and choice. Compatibility is a starting point, not a promise.
• Reading hard aspects as a sign of a breakup. Squares and oppositions create tension, but they are where a couple changes each other most.
• Reading someone’s intentions from synastry. A comparison describes the dynamic between two people, not what one of them thinks or will do.
• Comparing once and leaving it. Relationships change, and people learn each other’s language over time. Looking at the same comparison a year later shows what has become easier.
• Interpreting houses without birth times. If the time is unknown, leave the rising sign and house comparison out.

Where to go from here

The easiest way to begin looking at a relationship through astrology is to write two people’s big three side by side. Get to know your own big three first, then write those of a partner, a friend or a family member and compare the elements. After each comparison, note one “easy area” and one “work area”.

To compare two people’s rhythm, open the Compatibility tool in the Larisa app: next to your own birth details, enter the other person’s birth date, place and, if you know it, time; the tool compares the two birth charts in the language of relationships. Before reading the result, write your own comparison in one sentence using the steps above.

The big three are covered in detail in Sun, Moon and rising signs, and reading a single chart in how to read a birth chart. To look at the same relationship with cards, love tarot reading walks through the Relationship spread step by step, and for reading it through people and signs, see Katina love reading.