Synastry Calculator — Real Compatibility Astrology
Synastry is the classic two-chart compatibility technique: rather than merging two people into one chart, it lays both real natal charts side by side and measures every meaningful angle one person's planets form to the other's. Enter both birth details and every aspect — conjunction, trine, square, sextile, opposition — is computed from real planetary longitudes, not a sun-sign matchup table.
Frequently Asked Questions
What's the difference between synastry and a composite chart?
Synastry compares two real charts side by side and looks at the angles one person's planets form to the other's — it never merges the charts. A composite chart instead builds a single new chart from the midpoint of each planet pair.
What counts as a 'good' synastry aspect?
Traditional astrology reads trines, sextiles, and conjunctions as harmonious — ease and instinctive understanding — and squares and oppositions as tense friction. Neither is automatically good or bad; hard aspects are traditionally read as where real growth happens between two people, not simply as a warning sign.
Does synastry need both people's exact birth times?
Yes, for full accuracy. This tool computes each person's real planetary positions from their birth data, then finds every meaningful cross-chart angle within a real orb — an inaccurate time can shift house placements and tighten or loosen orbs on close aspects.
Why does my Venus-Sun synastry aspect matter more than others?
Traditional synastry treats contacts to the personal planets (Sun, Moon, Venus, Mars, Mercury) as the most personally felt points of contact, since these describe attraction, ease, and daily temperament rather than slower background themes.
Can synastry predict if a relationship will work?
No — it's a traditional interpretive framework describing where two charts naturally connect or create friction, not a scientifically validated predictor of relationship outcomes.