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, points and houses to look at

• The Sun and Moon: identity and emotional needs. Traditionally, contacts between them are read as a sign of natural ease or familiarity.
• Venus and Mars: Venus describes affection, values and what you enjoy together. Mars describes desire, drive and how you each respond to challenge. Contacts between them are the classic indicators of attraction.
• 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 and Neptune: slower themes, such as excitement and change, or idealisation and confusion. They tend to matter most when they touch a personal planet or an angle in the other chart.
• Pluto: intensity, fascination, power and transformation. Pluto contacts are often the ones people remember, and they are rarely casual.
• The Ascendant and Midheaven: the Ascendant shows first impressions and how each of you meets the other. The Midheaven shows shared ambitions and how you see each other's goals.
• The lunar nodes: a sense of familiarity, and the lessons a connection seems to carry.
• The houses: where your planets fall in the other person's chart shows which area of life you touch in them, such as home, work, friendship or intimacy, and the reverse.

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 do some people feel familiar within minutes, while others unsettle us in ways we can't quite explain? Synastry looks at where one person's planets fall in another's chart, and the character of a connection often shows itself in those crossings.

Venus and Mars contacts speak of attraction and desire. Moon and Ascendant contacts describe how seen, safe and understood each person feels. Saturn brings commitment and caution, and can steady a bond or weigh on it. Pluto contacts are often the ones people remember: magnetic, intense and rarely casual. How a contact plays out depends on the planets involved, the houses they touch and how closely they connect, which is why astrologers read the whole pattern rather than any single aspect.

The challenging aspects deserve as much attention as the harmonious ones. A square or opposition often marks the place where two people want different things, or need the same thing in different ways. Ease can bring comfort, and sometimes complacency. Friction can bring tension, and sometimes growth. Knowing where the difference lies gives you room for patience, clearer words and a wider view, rather than reading every hard aspect as a bad sign.

Synastry can also tell you about yourself. The same kinds of contacts tend to return in the connections that matter most to us, and they often trace back to our own chart: the planets that draw us in, the sensitivities other people touch. Read alongside your birth chart, synastry can show the qualities you keep being drawn to, the dynamics that come round again, and the sides of yourself that particular people bring out.

What it can't do is tell you whether a relationship will last, or decide anything for you. What it offers is a closer reading of the connection: where it comes easily, where it asks something of you both, and what it may be pointing towards.

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.