Synastry: How to Compare Two Birth Charts
Compare two charts →Free, no sign-up
Quick answer: Synastry overlays two birth charts and looks at two things: the aspects between your planets and theirs, and which of your houses their planets fall into. The key contacts are between the Sun, Moon, Venus, Mars and Ascendant.
The five contacts to check first
| Contact | What it shows |
|---|---|
| Sun–Moon | Whether one person's self meets the other's emotional needs; the base of long-term bonds |
| Venus–Mars | Attraction and romance |
| Moon–Moon | Emotional rhythm and daily habits |
| Mercury–Mercury | Whether you can talk, and whether arguments spiral |
| Saturn–personal planets | Commitment and responsibility, sometimes pressure and control |
Conjunctions, trines and sextiles usually make interaction feel natural; squares and oppositions bring tension, which can be spark or friction.
Their planets in your houses
Place the other person's planets in your houses to see which part of your life they touch. Their Venus in your 7th house: you may see them as an ideal partner. Their Saturn on your 1st house: you may feel watched and held to standards, but also safer.
Synastry vs. composite charts
Synastry shows how two people affect each other. A composite chart takes the midpoints of both people's planets to make one chart for the relationship itself. For a first look, synastry is enough.
Tips
- Read both directions: A's Venus to B's Mars is not the same as B's Venus to A's Mars.
- Tighten the orbs: synastry usually uses tighter orbs than a birth chart; within about 5° counts as clear.
- One hard aspect decides nothing; see whether ease or tension dominates overall.
FAQ
Can we do synastry without birth times?
You can read most planetary aspects, but not the Ascendant or houses, and the Moon may be off.
How is Sun-sign matching related to synastry?
Sun-sign matching is just one Sun–Sun contact in a synastry chart, so it says very little.
Are couples with many hard aspects doomed?
No. Tension also means attraction and growth; what matters is whether both are willing to work at it.