Free synastry
calculator.
Drop in two birth charts. We compute the angular relationships between your ten planets and theirs. Top five aspects ranked, scored, and translated. No pay-to-unlock. No horoscope-speak.
Run synastry now →What you get back
- Compatibility geometry score (0–100)
- Top 5 inter-aspects ranked by orb tightness × planetary weight
- One-line verdict for each aspect (no ‘you'll meet a stranger' nonsense)
- Compositive synastry wheel — both charts overlaid in color
- Downloadable PNG share card
Why ‘synastry score’ is honest geometry, not vibes
Most compatibility tests are quizzes. You answer 12 questions about your favorite color and they compute a percentage. Synastry is different: it's the actual angles between two people's natal planets — math, deterministic, falsifiable.
A Venus square Mars between you and your partner means something specific: attraction with friction, sexual chemistry that argues. A Sun trine Moon means smoothness, mirroring, easy emotional read. We compute every cross-aspect, weight it by orb and planetary importance, and give you a number you can trust.
What it is NOT
It's not prediction. It's not a love-meter. It doesn't care about your sun signs alone (sun-sign ‘compatibility’ lists are pop-magazine fluff). It doesn't replace knowing each other.
It's a starting point for honest conversation: here's the geometry, here's where it tends to go, what does that match in our actual experience? Useful only if you're willing to look.
FAQ
What is synastry?
Synastry is the geometry of two natal charts overlaid. Where your planets aspect their planets — that's the relationship pattern. A trine between your Venus and their Mars is different from a square. The math doesn't care if you're dating; it works for friends, family, coworkers, and your ex.
Do I need both birth times?
Helpful but not required. Sun, moon, and outer planets compute fine without time. Without time, ascendants and houses are uncertain — synastry still has signal because most aspects come from planet-to-planet positions, not house overlays.
How is the compatibility score calculated?
We weight each cross-aspect by orb tightness × planetary weight. A Sun-Moon trine within 1° counts more than a Mercury-Pluto sextile within 5°. The score is a 0–100 normalization. Above 70 = strong harmonic geometry. Below 40 = mostly dynamic / friction-heavy. Both are workable — they just feel different.
Will it tell me if we're meant to be?
No. Synastry shows the geometric pattern between two charts. What you do with it is yours. People with high scores break up; people with low scores stay forever. The chart describes, it doesn't decide.
Can I share my synastry result?
Yes — there's a 'Save card' button after each calculation that downloads a 1200×630 PNG with both names, your score, and the top aspect. Drop it in IG Stories, Threads, or your group chat.
✦ Different stars, mapping me. — Starlore