Synastry basics: compatibility beyond your Sun signs

"Are Scorpio and Gemini compatible?" It is one of the most searched questions in astrology, and also one of the hardest to answer well. Sun sign compatibility can offer a fun first impression, but two people are far more than two Sun signs.

Astrologers use a method called synastry to look at compatibility in depth. Instead of comparing one placement, it compares two full birth charts and asks how they interact. This guide explains how synastry works, which connections matter most and how to read the results with a balanced eye.

What is synastry?

Synastry is the art of laying one birth chart over another. You take the positions of one person's Sun, Moon, planets and Ascendant, and look at how they relate to the positions in the other person's chart.

The main tool is the aspect: the angle between a planet in your chart and a planet in theirs. If your Moon sits close to their Venus, or your Mars forms a square to their Sun, those contacts describe a particular kind of chemistry between you.

Synastry shows the dynamics of a connection: where it flows easily, where it sparks, where it may rub. It describes the relationship as a meeting of two people, each bringing their own chart to the table.

Why Sun signs are not enough

Your Sun sign describes your core identity, but a relationship involves much more than identity. It involves emotional needs (the Moon), attraction and affection (Venus), desire and drive (Mars), communication (Mercury) and how you come across day to day (the Ascendant).

Two people with "incompatible" Sun signs can share deeply harmonious Moon and Venus contacts. Two people with "perfect" Sun signs can find that their emotional styles clash. That is why many astrologers treat Sun sign compatibility as a starting point at most.

The contacts that matter most

Not every connection between two charts carries the same weight. These are the placements astrologers usually look at first.

Sun contacts: recognition and support

When one person's Sun connects with the other's Sun, Moon or Ascendant, there is often a sense of recognition, as if each person sees and supports who the other is. Sun to Moon contacts in particular are a classic indicator of mutual understanding.

Moon contacts: emotional comfort

The Moon describes emotional needs and instincts. When Moons connect harmoniously, or when one person's Moon touches the other's Sun or Venus, the relationship often feels safe and familiar. For more, see our guide to Moon sign compatibility.

Venus contacts: affection and attraction

Venus is the planet of love, beauty and pleasure. When one person's Venus connects with the other's Sun, Moon, Mars or Ascendant, there is often natural warmth and enjoyment of each other's company. Our guide to your Venus sign explains what Venus says about your style of love.

Mars contacts: desire and drive

Mars describes energy, desire and how you pursue what you want. Venus and Mars contacts between two charts are a traditional signature of physical attraction. Mars contacts can also bring friction: the same energy that creates sparks can create arguments, depending on the aspect.

Ascendant contacts: first impressions and ease

When a planet in one chart falls on or near the other person's Ascendant, that planet's qualities can shape how each person experiences the other. A partner's Sun or Venus on your Ascendant, for example, can feel like instant warmth and visibility. Because the Ascendant depends on birth time, these contacts are only reliable when both times are known.

Harmonious and tense aspects

The angle between two planets colors how they interact. The main aspects in synastry are:

• Conjunction (0 degrees). The two planets blend. Powerful and personal, its tone depends on the planets involved.
• Sextile (60 degrees). Friendly and cooperative. An opportunity for ease that grows with effort.
• Trine (120 degrees). Natural harmony and flow. Things tend to feel easy here.
• Square (90 degrees). Tension and challenge. Squares can create friction, but also motivation and attraction.
• Opposition (180 degrees). A pull between opposites. Often magnetic, sometimes polarizing, and frequently where couples learn the most from each other.

It is tempting to read trines as "good" and squares as "bad," but a relationship with only easy aspects can lack spark, while tense aspects often provide the energy that keeps a connection alive. Many lasting relationships contain both. What matters is how the two people handle the tension.

Reading synastry with a balanced eye

A few principles keep synastry useful and grounded:

Look for patterns, not single aspects. One difficult contact does not define a relationship, and one lovely contact does not guarantee one. Look at the overall picture and the themes that repeat.

Remember it goes both ways. Your Venus touching their Mars is one connection. Their Venus touching your Mars is another. Synastry describes how each person experiences the other, which may not be identical.

Combine synastry with each person's own chart. A contact means different things depending on the individual charts behind it. Someone with a very independent Moon may experience a strong Moon contact differently from someone who craves closeness.

Let the chart start the conversation. The most useful thing synastry can do is give you language to discuss what you each need, where you click and where you clash.

Why no single score decides a relationship

Many compatibility tools offer a percentage or a rating. These can be fun, and they summarize a general tone, but no number can capture what two people bring to each other. Relationships are shaped by choices, communication, timing, shared values and countless things a chart does not describe.

Synastry is best understood as a description of potential dynamics, not a prediction of how a relationship will go or what another person will do. A challenging synastry can describe a deeply loving bond between two people who understand each other's differences. A harmonious one still needs care.

What you need to compare two charts

To see synastry in full, you need the birth date, place and ideally the time for both people. Without birth times, you can still compare the Sun, the planets and usually the Moon, but the Ascendant and house overlays will be uncertain. Our guide on finding your birth time can help.

See your two charts side by side

Whether you are curious about a new connection or want to understand a long relationship more deeply, synastry offers a richer picture than any Sun sign match. I lay two charts side by side and walk through the contacts that shape your connection.

Enter both sets of birth details and see what your charts say about each other.