What Is Synastry? How Two Charts Are Compared
Synastry is the astrological technique that reads the relationship between two people by laying their birth charts over each other. It looks at the aspects one person's planets make to the other's planets and at which of the other's houses they fall into. It is far more detailed than sign compatibility: instead of asking "Do Aries and Libra get along?", it shows where two charts feed each other and where they rub.
Compare two charts
Relationship analysis through cross aspects, house overlays, declination and antiscia contacts.
What synastry looks at
Cross aspects are the heart of synastry. If one person's Venus is conjunct the other's Mars, there is a strong attraction. If one person's Moon trines the other's Sun, emotional harmony and ease are read. If one person's Saturn squares the other's Moon, the relationship is binding but can sometimes feel heavy.
House overlays show which area of life the relationship is lived in. If one person's planets fall into the other's 7th house, partnership and marriage come to the fore; the 4th house brings a feeling of home and family; the 10th, career or public visibility.
There are subtler contacts too. Declination parallels mean two planets standing at the same height in the sky, creating a bond similar to a conjunction. Antiscia means two points mirroring each other across the solstice axis; it describes bonds that are not obvious but are felt. These never appear in sign compatibility tables.
Does a good match have no hard aspects?
It does have them. A synastry with no hard aspects at all is comfortable but often sleepy; the two people do not change each other. Charts of long relationships usually contain both supportive and challenging contacts together. What matters is where the difficulty sits and whether there are supportive bonds to carry it.
That is why synastry cannot be summed up in a single score. A result like "you are 70 percent compatible" ignores the real complexity of two charts.
Synastry, composite and Davison
Synastry compares two separate charts: how I touch you, how you touch me. A composite chart creates a single chart from the midpoints of the two charts and reads the relationship itself, as if it were an entity independent of both people. A Davison chart also builds a single chart for the relationship, but does it by calculating a real moment exactly between the two birth times and the two birthplaces.
The three complement each other. Synastry shows who does what to whom; the composite and Davison describe the relationship's own character.
Synastry in FalAstry
You enter both people's birth details. Both charts are calculated from real ephemeris data; cross aspects, house overlays in both directions, declination parallels and antiscia contacts are extracted one by one. The interpretation is built on these computed contacts and describes both the supportive and the challenging sides together.
Composite and Davison charts are available as separate tools if you want to look at the relationship itself.
Frequently asked questions
Do both people need a birth time for synastry?
For the most accurate result, yes. Without a time, house overlays cannot be read; the cross aspects still come out largely correct.
Is sign compatibility the same as synastry?
No. Sign compatibility looks only at two Sun signs. Synastry reads all the planets, houses and the aspects between them across both charts.
Does synastry say whether a relationship will last?
It does not give a definite outcome. It shows where things are easy and where there is friction. How the relationship goes depends on what the two people do with these contacts.
Is synastry only for couples?
No. Friendships, business partnerships, family relationships and the bond between a parent and a child are also read through synastry.
Compare two charts
Relationship analysis through cross aspects, house overlays, declination and antiscia contacts.