The full synastry guide
Read the guide
Relationship astrology · The free Snapshot
Understand the patterns between you.
A little perspective on how two people communicate, show care and get things started—with a question or small thing to try. Read your first insight straight away. A free account opens and saves the rest.
About 2 minutes · free account · no payment needed
Connection Snapshot
Start with two people.
Add a first name and birth date for each person. Read first; choose whether to save afterwards. If you don't know a birth time, leave it unknown.
What goes into a Snapshot?
We compare Sun, Mercury, Venus and Mars signs from both birth dates. We leave out any sign that might have changed during an unknown birth time.
- Connection
- First person
- Second person
- Snapshot
Synastry essentials
Two charts, held in conversation.
Synastry is the branch of astrology that compares two birth charts to describe how two people meet: what flows, what grates, and what each person tends to notice first. A full synastry chart weighs planets, angles, houses and aspects together. The free calculator above is deliberately narrower — it reads only stable Sun, Mercury, Venus and Mars signs, and says plainly what it could not establish.
The six contacts that matter
Where connection shows up.
Synastry contact
Sun to Sun
- How two people recognise each other’s basic direction and sense of self.
Synastry contact
Moon contacts
- Emotional habits, comfort and what each person needs to feel settled. Time-sensitive, so a fuller reading needs verified birth times.
Synastry contact
Mercury contacts
- How information, humour and disagreement travel between two people.
Synastry contact
Venus contacts
- Taste, affection, appreciation and what each person treats as care.
Synastry contact
Mars contacts
- Drive, initiative, irritation and how the two handle effort and conflict.
Synastry contact
Angles and house overlays
- Where one person’s planets land in the other’s chart. Entirely dependent on accurate birth time and place.
Reading with care
Evidence before interpretation.
01
Begin with the bond
Relationship context shapes the language; it does not decide an outcome.
02
Use real birth dates
The calculator works from each real birth date and never substitutes noon for a missing time.
03
Keep uncertainty visible
If a sign could have changed within the possible birth window, it is left open.
04
Read reflectively
Observations are prompts to compare with real life, never labels or guarantees.
Every relationship
Synastry goes beyond romance.
The chart comparison is the same; the emphasis and the language change with the bond.
Romantic partners
Venus, Mars and Sun contacts describe recognition, taste and pace — read as reflection, not as a score or forecast.
Parent and child
Moon and Mercury contacts describe attunement and communication, in neutral role-aware language without age assumptions.
Siblings
Mercury and Mars help explain closeness, different rhythms and where effort is shared.
Close friends
Venus and Jupiter contacts describe shared values, humour and what each person appreciates.
Compare
Synastry or composite?
They answer different questions. Use synastry to understand how two people affect one another; use a composite chart to understand the relationship as a shared entity. Neither is calculated by the free tool above.
Synastry chart
Two charts side by side, showing each person’s experience of the other, including where they pull in different directions.
Composite chart
One midpoint chart describing the relationship’s own themes, purpose and shared patterns.
A fuller synastry chart
What deeper chart work can consider.
With verified birth times and places, a fuller reading can examine cross-chart aspects, the Moon, angles and houses. Those are outside the free calculator above and are never approximated there.
Planetary aspects
Calculated angular relationships between two sets of placements.
Moon and angles
Time-sensitive placements that should be omitted when the birth time is uncertain.
House overlays
Birth-time and location-dependent context that requires verified inputs.
Synastry questions
Frequently asked questions.
A synastry chart compares two birth charts side by side. It is a symbolic way to reflect on how two sets of planetary placements meet; it is not a scientific test or a prediction of what a relationship will do.
The calculator on this page compares stable Sun, Mercury, Venus and Mars signs for two people and turns them into a few plain-language observations. It does not calculate cross-chart aspects, the Moon, houses, angles, retrograde motion or timing, and it does not produce a compatibility score.
No. If a birth time or birthplace timezone is unavailable, the calculator checks the whole birth date across every world timezone. Anything that changes sign inside that window is left open rather than approximated.
An observation only appears when both people have steady evidence for that theme. Uncertainty is never dropped to reach a particular number of cards.
Synastry is reflective astrology, not a scientific measurement. Accurate birth details support more specific chart work, but no chart guarantees an outcome or replaces what two people know about their own relationship.
Synastry keeps two charts separate and looks at how each person experiences the other. A composite chart merges the two into one midpoint chart and describes the relationship as a single shared entity.
Yes. The same chart-comparison method is used reflectively for partners, parents and children, siblings, friends and other close connections. The language should always fit the relationship.
Your details stay in this browser until you choose an account step. If you are signed out, creating a free account or signing in from the finished Snapshot saves it and both people privately in My People. Once signed in, each new Snapshot offers a separate choice about what to keep. Nothing is shared with the other person and nobody is notified.
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