Synastry: How Two Charts Meet

Every birth chart describes one person. Synastry is what astrologers use to look at two at once: it lays one chart over the other to see how they meet.

What synastry compares

Two things. The first is the aspects between the charts: the angles formed between one person's planets and the other's, such as your Venus trine their Moon. The second is the house overlays: which of their houses your planets fall in, and the reverse. Aspects show how the planets interact. Houses show which areas of life are touched.

The comparison runs both ways. Their Mars meeting your Moon is a different experience for each of you, so synastry looks at the contacts from both sides.

The planets that carry the most weight

• The Sun and Moon: identity and emotional needs. Contacts between them often make a connection feel as though it fits.
• Venus and Mars: attraction, affection, desire, and how each of you goes after what you want.
• Mercury: how you talk, listen and think things through together.
• Saturn: commitment and responsibility, and where a relationship feels steadying or restrictive.
• Jupiter: encouragement, generosity and growth.
• Uranus, Neptune and Pluto: slower, more intense themes, such as excitement and change, idealisation or confusion, and depth or power. When they touch a personal planet in the other chart, the effect can be strong.
• The Ascendant, Midheaven and lunar nodes: first impressions and how you appear together, public direction, and familiar patterns.

Reading the aspects

Conjunctions blend two planets. Trines and sextiles are traditionally associated with ease, squares and oppositions with tension and difference. Tension isn't a verdict: many lasting relationships rest on a square or an opposition that gives two people something to work with. Look at the tightest aspects first, and at themes that repeat, since several contacts pointing the same way matter more than one on its own.

What synastry can tell you

Why are you drawn to certain people? Why do some connections feel effortless, while others bring out feelings or reactions you didn't expect? Synastry explores the astrological connections between two birth charts, offering another way to understand what happens when two people come together.

Pluto contacts can point to themes of intensity, fascination and transformation. Venus and Mars can shed light on attraction and desire, while Moon and Ascendant contacts add insight into emotional responses and the way two people experience each other. Sometimes the connections are easy to recognise. Others take a little more understanding.

The challenging aspects can be just as revealing as the harmonious ones. They may highlight differences in emotional needs, communication or the way each person approaches a situation. Understanding these patterns can help you recognise where patience, clearer communication or a different perspective might make a difference, rather than seeing every difficult aspect as a bad sign.

Synastry can also reveal patterns in your own relationships. You may begin to notice the qualities you're repeatedly drawn to, the dynamics that keep returning, or the sides of yourself that certain people bring out. Looking at these connections alongside your own birth chart can help you understand yourself as well as the other person.

Synastry can't tell you whether a relationship will last or make decisions for you. What it can offer is a deeper understanding of the connection, its challenges and its potential, giving you more to reflect on as you work out what it means to you.

Where to begin

1. Get to know your own chart first. Our guide to reading a birth chart is the place to start.
2. Compare the Sun, Moon, Venus and Mars across the two charts.
3. Look at the tightest aspects, then the house overlays.

Our free synastry calculator draws both charts and lists every aspect between them, and the aspect finder explains what each pair of planets means.