What is synastry?
Synastry is the branch of astrology that compares two birth charts to study the connections between them. By measuring the aspects, the angles, between the planets of one chart and the planets of the other, it maps where two people meet with ease and where they meet friction.
How the synastry calculator works
Enter the birth date and city for two people, and a birth time if you have it to sharpen the Moon and the chart angles. The tool builds both charts on Swiss Ephemeris astronomy, then finds the major aspects between the two sets of planets, sorted by how exact each one is.
Reading the aspects between two charts
Trines and sextiles tend to describe flow and ease; squares and oppositions describe tension that can drive growth; conjunctions blend two energies together. The mix is a portrait of a connection, not a score and not a verdict on whether a relationship will last.
Synastry and privacy
This is a free tool with no account required. The names you enter stay in your browser and are never sent anywhere, only the birth dates and cities are used to compute the charts. For a deeper written reading, explore the synastry articles in the AstrologyWiki wiki.