Synastry Chart Calculator

Synastry compares two natal charts to see how their planets interact across both people. It surfaces compatibility patterns — emotional fit, sexual chemistry, communication style, friction points — that single-sign compatibility (just Sun signs) cannot.

Yes — completely free with full interpretations. No signup, no email, no paywall. Calculate unlimited synastry charts.

Sun-Moon (emotional resonance), Venus-Mars (attraction and desire), Moon-Moon (emotional rhythm), Saturn-Venus (commitment vs. restriction), and Mercury-Mercury (communication style) are the heaviest hitters. Hard aspects (squares, oppositions) bring growth tension; soft aspects (trines, sextiles) bring ease.

For planetary aspects, no — date and place are enough. For Ascendant, Midheaven, and house overlays (where each person's planets land in the other's houses), exact birth times are required for both people.

Synastry compares two separate charts; the composite chart merges both into a single chart representing the relationship itself as an entity. They answer different questions — synastry shows how you interact, composite shows what the relationship is.

Both charts use the same calculation path as the birth chart calculator. Planet positions and aspect orbs are validated against the project accuracy contract rather than estimated from sun signs.