Free synastry chart
Synastry chart calculator
Enter two birth details and we calculate both natal charts, find every aspect between them, and weigh the whole synastry into one score across five dimensions. Your strongest contacts, named from real placements.
What a synastry chart is
A synastry chart lays your birth chart over someone else's, so both sets of planets share one wheel. Astrology then reads the angles each of your planets makes to each of theirs. Those angles are called inter-aspects, and they are the raw material of relationship astrology: your Moon trine their Venus tends to feel like easy affection, while your Mars square their Saturn can feel like driving with the handbrake on. No single aspect decides anything. A real synastry reading weighs dozens of contacts at once, which is exactly what the calculator above does with your two charts.
The aspects we count, and what they weigh
Most calculators are a black box. Ours is not: these are the six aspects we score, with the exact orbs we allow. An orb is how far from the exact angle a contact can drift and still count; the tighter the orb, the more the aspect weighs. Because the Sun and Moon are the loudest voices in any chart, contacts involving a luminary get two extra degrees of orb. And aspects between two outer planets, Uranus, Neptune, and Pluto, are skipped entirely: whole generations share them, so they say nothing about the two of you.
Conjunction
0°
orb 8° · reads as harmony
Two planets in the same spot. Their agendas merge, for better or worse.
Sextile
60°
orb 6° · reads as harmony
A friendly, cooperative angle. Opportunity that still wants a nudge.
Trine
120°
orb 8° · reads as harmony
The flowing angle. Things work between you without either of you trying.
Square
90°
orb 7° · reads as friction
The working angle. Friction that pushes both of you to grow.
Opposition
180°
orb 8° · reads as friction
Face to face across the wheel. Magnetic, polarizing, asking for balance.
Quincunx
150°
orb 3° · reads as friction
The awkward angle. Small chronic adjustments that never feel finished.
One deliberate exception: Sun-Moon conjunctions and oppositions read as harmony even though the geometry is hard. The luminaries fitting together is the single most cited compatibility contact in synastry, and we score it that way.
Five dimensions instead of one number
A single score hides more than it shows, so every aspect we find is routed to the part of the relationship it actually describes. The overall number is the summary; the five dimensions are the story.
Attraction
Venus-Mars, Mars-Mars, and Sun-Mars contacts: spark, desire, and pace.
Emotional
Every aspect touching either Moon: moods, safety, and what home feels like.
Communication
Every aspect touching either Mercury: how you talk, argue, and repair.
Stability
Every aspect touching either Saturn: commitment, structure, and staying power.
Growth
Jupiter contacts plus Sun-Sun: optimism, luck, and where you expand each other.
Synastry chart vs composite chart
Synastry and composite charts answer different questions. Synastry compares your two charts aspect by aspect and describes how you experience each other, day to day and skin to skin. A composite chart collapses both charts into a single third chart built from midpoints, and treats the relationship itself as the subject. Both are legitimate tools, but synastry is where compatibility work starts, so your free score above is pure synastry: two real charts and every meaningful angle between them.
Synastry questions, answered
How the chart is calculated and what the numbers mean.
Is this synastry chart calculator free?+
Yes. Enter both people’s birth details and you get the full result free: a compatibility score, five dimension scores, and your strongest synastry aspects named from your real placements. No email and no account are needed to see it.
What is a synastry chart?+
A synastry chart lays one person’s birth chart over another’s and reads the angles, called aspects, that each planet in one chart makes to each planet in the other. Those inter-aspects describe how two people experience each other: where affection flows easily, where friction lives, and what holds over time.
Which synastry aspects matter most?+
Sun-Moon contacts are the classic marker of a couple that fits, which is why we read even the hard Sun-Moon angles as harmony. After the luminaries, look at Venus-Mars for attraction, Moon-Moon for emotional rhythm, Mercury contacts for communication, and Saturn contacts for whether it lasts. The tighter the orb, the louder the aspect.
What is the difference between synastry and a composite chart?+
Synastry compares two charts aspect by aspect and describes how you experience each other. A composite chart builds a single third chart from the midpoints of both and describes the relationship as its own entity. Synastry is the tradition’s primary tool for compatibility, so that is what your free score is built on.
Do we both need exact birth times?+
Exact times give the truest result because the Moon moves quickly and the houses turn all day. If one time is uncertain, enter your best estimate: most of the score comes from slower moving placements, so the result is still meaningful, just treat it as an estimate until the time is confirmed.
What does the paid reading add?+
The free chart tells you what is there; the reading explains what it means for the two of you. It is a long, specific write-up of your synastry across all five dimensions, written from your actual placements. It costs £9.00 once, arrives by email, and is yours to keep and download.
Compatibility by zodiac sign
Aries pairings
Taurus pairings
Gemini pairings
Cancer pairings
Leo pairings
Virgo pairings
Libra pairings
Scorpio pairings
Sagittarius pairings
Capricorn pairings
Aquarius pairings