Synastry chart calculator
Compare two real birth charts, not just two Sun signs: attraction, emotional bond, communication and staying power. Free.
What synastry is
Synastry is the comparison of two birth charts. Instead of asking whether a Leo suits an Aquarius, it looks at how one person's Sun, Moon, Venus and Mars meet the other's. A Moon close to a partner's Sun, or Venus opposite Mars, tells far more about a couple than the two Sun signs do.
We compute the angles between the two charts, weigh them by how much each planet matters in love, and summarise them in four dimensions with an overall score.
How to read the result
A high score means ease, not a guarantee; a lower one means the relationship asks for more conscious effort. Tense contacts are also where attraction lives. With birth time and place for both people we add the rising signs and a precise Moon, and the reading becomes sharper.
Questions
Do I need the birth time for synastry?
No. Dates alone give a solid reading of Sun, Mercury, Venus and Mars, and usually the Moon. Adding the time and place for each person brings in the ascendant and fixes the Moon's exact degree, which makes the emotional part more reliable.
Which contacts matter most in synastry?
Sun to Moon, Venus to Mars and Moon to Moon carry the most weight for romantic compatibility. Saturn contacts say a lot about how long a bond lasts, and Mercury contacts about how easily two people talk.