Synastry Chart Calculator
Two birth charts, side by side. The real connections between you, with a compatibility reading.
Person one
Person two
Calculated in your browser. Your birth details are never stored.
What is a synastry chart?
A synastry chart compares two birth charts to read the connection between two people. Where a single birth chart maps one person's sky, synastry lays two charts over one another and looks at how the planets speak to each other: the easy, supportive contacts, the magnetic ones, and the places that ask for patience. It is the astrology of relationships, used for romance, friendship and family alike.
How synastry works
The heart of synastry is the aspects between the two charts, the angles one person's planets make to the other's. A trine or sextile is read as ease and flow, a conjunction as a powerful blending, and a square or opposition as a charged, growth-bringing tension. This calculator finds every major contact between your planets, describes it in plain language, and weighs them into a compatibility reading. The most telling contacts involve the Sun, Moon, Venus, Mars and the Ascendant, so those carry the most weight.
The compatibility score
The score is a gentle summary, not a verdict. It weighs the harmonious contacts against the challenging ones, giving more weight to the planets that matter most in relationships. A high score points to natural ease; a lower one simply means more of the connection is built through effort and growth. Every pairing has both. A score has never decided a relationship, and it never will.
A gentle note
Synastry is a mirror for reflection, not a test to pass or fail. Charts that look effortless can drift, and charts full of friction can build something deep and lasting, because real relationships are made of attention, kindness and choice, not angles. Read your synastry as a way to understand each other more tenderly, and take what is useful.
Synastry FAQ
What is the most important aspect in synastry?
Contacts between the Sun, Moon, Venus, Mars and the Ascendant are usually read as the most telling. Sun and Moon contacts speak to a deep sense of being seen, while Venus and Mars carry attraction and warmth.
Do we both need our birth times?
No, but they help. Without a birth time you still get every planet-to-planet aspect, which is the core of synastry. A birth time adds the Ascendant, the Midheaven and the houses each person's planets fall in for the other.
Is a high synastry score better?
A higher score points to more natural ease, and a lower one to more growth through effort, but neither decides a relationship. Some of the deepest bonds are full of challenging aspects that two people choose to work with.
Can I use synastry for friendship or family?
Yes. Synastry reads any close connection, not only romance. The same contacts describe the warmth, the ease and the friction between friends, parents, children and colleagues.
Is synastry real?
Synastry is a reflective tradition rather than a science. There is no evidence the planets shape a relationship, but many people find it a meaningful, tender way to understand one another. Enjoy it as a mirror, not a forecast.