Discover your astrological synastry
Enter the birth details of two people and discover how their natal charts align. Real astronomical calculation via Swiss Ephemeris, cross-aspects between both maps and composite chart by midpoints.
What is synastry?
Synastry is the astrological study of compatibility between two people by cross-referencing the planetary positions of their natal charts. Unlike sun-sign compatibility —which only compares the birth month—, synastry considers the ten planets, the angles (Ascendant, Midheaven), the lunar nodes and, optionally, asteroids such as Chiron, Ceres, Pallas, Juno and Vesta.
This calculator uses Swiss Ephemeris, the same astronomical engine used by professional astrology software. For each planet its real ecliptic longitude at the moment of birth is calculated, and then aspects (conjunction, sextile, square, trine, opposition) are searched between the planets of both charts. The maximum orb is 8 degrees for conjunctions and oppositions, 7 for trines and 6 for sextiles and squares.
The compatibility score (0-100) is calculated by weighting each aspect according to the pair of planets involved: Venus-Mars and Sun-Moon have the highest weight, followed by Moon-Venus and Sun-Venus. Harmonious aspects (trine, sextile, soft conjunction) add; tense aspects (square, opposition) subtract. The result is presented in four categories: Love and Attraction, Communication, Energy and Passion, Karma and Growth.