Synastry Chart Calculator

Synastry is the comparison of two birth charts. Rather than reading either person on their own, it looks at the angles between one person's planets and the other's: your Venus against their Mars, their Moon against your ascendant. Those inter-chart aspects are what the technique is about, and they are read as the specific texture of the relationship - where the two of you fit easily, where you rub, and which parts of each person the other reliably activates.

Direction matters here in a way it does not within a single chart. Your Venus on their Mars and their Venus on your Mars are two different statements: the first says something about how you find them attractive, the second about how they find you. A synastry grid that lists each pairing once has thrown away half the information. This calculator crosses both charts in full, and every row names which chart each body belongs to.

It also leaves the outer planets out, and that is deliberate. Uranus, Neptune and Pluto spend seven to thirty years in a sign, so two people born within a few years of each other share them almost exactly. An aspect between two Neptunes describes a generation rather than a couple, and including it fills the grid with contacts that carry no information about the pair. What remains are the personal planets, the angles and the node - the placements that genuinely differ between two people and that the tradition actually reads. Both charts need a birth time, since the ascendant and midheaven are among the most-read contacts in synastry.