Synastry: How Two Birth Charts Are Compared
Synastry is the comparison of two birth charts. Instead of matching Sun signs, it measures the aspects between one person's planets and the other's, and looks at where each person's planets fall in the other's houses. It is the most detailed way astrology describes a relationship.
Why Sun signs are only the start
Sun-sign compatibility compares two of the twenty or so points in each chart. Two people with clashing Sun signs can have Moons in harmony and Venus on Mars, and the reverse. Sign-pair guides are useful for the general shape; synastry fills in the detail.
The contacts that matter most
Conjunctions, oppositions and squares are the strongest contacts; trines and sextiles make things easy.
- Sun and Moon: identity meeting emotional needs, a classic sign of a lasting bond.
- Venus and Mars: attraction and desire.
- Moon and Moon: whether two people feel at home together.
- Mercury and Mercury: how easily you understand each other.
- Saturn to personal planets: commitment, duty and sometimes weight.
- Anything on the other person's rising sign or Descendant.
House overlays
If your Venus falls in someone's 7th house, you register in the part of their chart concerned with partnership. If your Saturn falls in their 4th, you bring structure, or pressure, to their home life. Overlays explain why two people can describe the same relationship very differently.
Composite charts
A composite chart takes the midpoint of each pair of planets and reads the relationship as its own entity. Synastry shows how two people affect each other; the composite shows what the relationship becomes.
Find yours
Enter two sets of birth details to see every aspect between the charts. Birth chart compatibility
Compare your actual charts
Sign compatibility gives the outline. Your two full charts give the relationship. Compare two birth charts