What is a synastry chart?

A synastry chart compares the planets and angles of two natal charts to study how the two people affect one another.

Does synastry prove that a relationship will last?

No. Synastry describes patterns and points of ease or friction; it cannot guarantee an outcome or replace communication and choice.

Synastry Chart Guide: Compare Two Birth Charts

What a synastry chart measures

A synastry chart places the planets of one person around the natal chart of another, revealing inter-chart aspects and house overlays.

It is not a single compatibility percentage. A useful reading asks how each connection behaves: which needs are supported, where expectations differ, and what kind of effort the bond requires.

A practical reading order

Start with each natal chart. A planet cannot behave in synastry separately from its natal condition.

Compare Sun, Moon and Ascendant. These describe identity, emotional rhythm and approach.

Read Venus and Mars. Look at affection, attraction, pursuit and conflict style.

Check Mercury. Communication aspects often explain whether differences can be discussed.

Add Saturn and the house overlays. These show responsibility, pressure, duration and where the bond lands in life.

Aspects are conversations, not grades

ConjunctionTwo functions become tightly linked and difficult to separate.

Trine / sextileEnergy tends to cooperate, though ease still requires use.

SquareFriction creates action, learning and recurring adjustment.

OppositionPolarization can bring attraction, projection and negotiation.

House overlays

When one person’s planet falls in another person’s seventh house, partnership themes become prominent; in the fourth, home and emotional roots; in the tenth, career or public direction. An overlay shows where the relationship is experienced, while aspects show how the two planetary functions interact.

What synastry cannot tell you

It cannot prove that two people are soulmates, guarantee marriage, or turn difficult behavior into destiny. Use it as a language for patterns—not as permission to ignore consent, safety or real-world evidence.

Synastry questions

Do both people need an exact birth time?

Exact times are needed for Ascendants and dependable house overlays. Without them, planetary aspects may still be compared, but angle and house conclusions should be limited.

Does AstroDice generate a bi-wheel synastry chart?

Not currently. This is an educational guide. You can generate each natal chart separately and use the focused love-reading tool for a specific question.

How to Read a Synastry Chart