How to read a synastry chart
Each line in the result is an aspect: an angle between one person’s planet and the other’s. Conjunctions merge two energies, trines and sextiles flow easily, and squares and oppositions create friction that can feel like chemistry or conflict. The tighter the orb (the distance from the exact angle), the stronger the contact.
The contacts astrologers look at first
- Moon and Sun
- One person’s identity meets the other’s emotional needs. Astrologers treat Sun–Moon contacts as one of the classic signatures of a lasting bond.
- Moon and Moon
- Your emotional rhythms and needs meet directly: how you comfort, react and feel at home.
- Mars and Venus
- The traditional signature of attraction and chemistry: desire meets affection.
- Ascendant and Venus
- Physical and aesthetic attraction: one person finds the other’s manner and look appealing.
- Saturn and Venus
- Love meets commitment and responsibility. Astrologers link these contacts with loyalty and staying power, and sometimes with feeling restricted.
- North Node and Sun
- Astrologers link Node contacts with a fated or purposeful feeling, as if the relationship moves you along your path.
House overlays
If you know the second person’s birth time, the calculator shows which of their houses your planets land in. Your Venus in their seventh house, for example, is read as you bringing affection into their idea of partnership. Each person’s planets in the other’s houses describe where you affect each other’s lives.
Questions
What is synastry?
Synastry is the astrological comparison of two birth charts. It looks at the angles (aspects) between one person’s planets and the other’s, and at which of each other’s houses the planets fall in.
Is this a compatibility score?
No. Astrologers read synastry as a pattern of strengths and tensions rather than a percentage. Challenging aspects such as squares often bring as much attraction and growth as easy trines, so the calculator shows the contacts rather than inventing a score.
Do we need exact birth times?
Not for most planet-to-planet aspects, which only need the dates. The Moon is the exception: it moves about 13 degrees a day, so without birth times its aspects, including Sun–Moon and Moon–Moon, can be off by several degrees. Birth times also add the Ascendant and the house overlays, which show where in life each person affects the other.
Which aspects matter most?
Traditionally Sun–Moon, Moon–Moon, Venus–Mars and contacts to the Ascendant are given the most weight, along with Saturn contacts for long-term commitment. These are listed first as key contacts.