Both birth dates
Set the planetary sky for Person A and Person B before any chart-to-chart comparison is made.
Synastry calculator
Birth Chart Compatibility Calculator
Compare two natal charts through genuine synastry calculations rather than a Sun-sign-only match or an unexplained compatibility percentage. AstroZora is designed to show the major aspects between two charts, relationship themes and house overlays when both birth times support them. If one or both times are unknown, time-sensitive angles and overlays are removed and uncertain planetary contacts are labeled instead of presented as exact.
Calculation first
No invented placements
Private session results
Quick answer
What does a birth chart compatibility calculator compare?
A synastry calculator compares the positions in one natal chart with the positions in another. It looks for chart-to-chart aspects such as conjunctions, trines, squares and oppositions, then groups the contacts into useful relationship themes. With two exact birth times it can also calculate where one person’s planets fall in the other person’s houses.
What you need
Two charts need two sets of birth details
Each person is calculated independently first. Accuracy in either chart affects which synastry layers can be included in the comparison.
Exact birth times
Allow precise Moon positions, Ascendant and Midheaven contacts, and reliable house overlays. Unknown times reduce the available layers.
Both birthplaces
Resolve coordinates and historical timezones so each recorded local birth time maps to the correct astronomical moment.
How it works
What AstroZora synastry is designed to show
The production endpoint returns named inter-chart aspects with exact or uncertainty-aware orbs, plus house overlays only when both charts support them. It also groups contacts into emotional connection, communication, attraction, relationship dynamics, long-term themes and potential friction. These are descriptive lanes, not six separate grades or a hidden universal score.
Read the AstroZora methodology
Your result can include
- Inter-chart major aspects
- Exact / confirmed / possible certainty
- Emotional connection
- Communication
- Attraction
- Long-term themes
- Potential friction
- House overlays when both times are exact
Accuracy & uncertainty
AstroZora shows what the data supports.
Birth time
Time-sensitive angles and houses are never presented as exact when the birth time is unknown.
Historical time
Birthplace data is resolved to an IANA timezone so historical offsets and daylight-saving transitions can be handled explicitly.
Calculation metadata
Results are designed to expose zodiac, house-system, ephemeris and timezone-version details for reproducibility.
Reading example
Read the contact before judging the relationship
If Person A’s Venus forms a trine to Person B’s Moon, the useful information is the two planets involved, the aspect type and how tight the orb is. That contact can contribute to an attraction or emotional-connection theme. It should not be converted into “82% compatible,” and it does not erase a separate Mercury square or Saturn opposition elsewhere in the comparison.
Learn the step-by-step reading methodCommon questions
Birth chart compatibility questions
Visible answers for users; no FAQ rich-result markup is added.
Is birth chart compatibility the same as Sun-sign compatibility?
No. Sun-sign matching compares one placement from each chart. Synastry compares many chart factors and the aspects formed between them.
Do I need both exact birth times?
Exact times are needed for Ascendant and Midheaven contacts and reliable house overlays. AstroZora can still compare supported planetary contacts when a time is unknown, but it labels uncertainty and removes unsupported layers.
Why does AstroZora not show one compatibility percentage?
A single number hides which contacts created it and implies a precision that the underlying interpretive method does not support. AstroZora exposes the actual aspects and theme counts instead.
Does a difficult aspect mean a relationship will fail?
No. Synastry is presented as a way to describe patterns of ease, tension and interaction, not as a verdict about whether two people should be together.
Go deeper when you are ready
Get My Full Compatibility Reading
Start with the actual chart-to-chart contacts, then explore how the emotional, communication, attraction and long-term themes fit together.
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