Short answer: Synastry compares two Western astrology charts using planetary positions and aspects. Bazi compatibility compares two Four Pillars charts using traditional element, stem and branch relationships. Both offer symbolic interpretations; neither establishes whether a relationship will succeed.
Relationship readings can use similar words while relying on different methods. Knowing the difference makes the results easier to discuss.
Synastry and Bazi compatibility both compare birth charts. Their categories and interpretation rules differ, so a result from one need not match a result from the other.
Here is what each method examines and how to use a comparison thoughtfully.
Synastry: comparing planetary relationships
Synastry compares the planetary positions in two birth charts. An interpretation may examine aspects between the charts and where one person's planets fall in the other's houses.
Astrologers may interpret Venus and Mars contacts through attraction, Moon contacts through emotional needs, and other aspects through ease or friction. These are symbolic associations, not evidence of how two people feel or behave.
A useful reading explains its symbols and turns them into questions you can discuss. It cannot replace what you learn through the relationship itself.
Bazi compatibility: comparing Four Pillars
Bazi compatibility compares two people's Four Pillars of Destiny charts. Each person has four pillars, year, month, day and hour, and each pillar carries a Heavenly Stem and an Earthly Branch tied to the five elements: wood, fire, earth, metal and water.
Traditional interpretations examine relationships between the stems, branches and elements of the two charts, including combinations and clashes. The Day Masters provide reference points within that interpretation.
A reading may also compare time periods. Words such as 'support' or 'clash' describe chart relationships; they do not establish whether daily life together will be easy or difficult.
Side by side
| Synastry (Western) | Bazi Compatibility (Chinese) | |
|---|---|---|
| Reads | Two charts overlaid, planet to planet | Two sets of four pillars, element to element |
| Typical topics | Planetary symbolism applied to attraction, needs and communication | Element and branch relationships, sometimes compared across time periods |
| Chart features | Venus and Mars contacts, moon links, North Node | Stem and branch relationships, elements and Day Masters |
| A useful reflection question | Which descriptions match the way we communicate? | Which differences in routine or priorities do we want to discuss? |
| Cannot establish | A person's feelings or a relationship's outcome | A person's feelings or a relationship's outcome |
How to compare the two
Choose a specific question, such as how you handle disagreements. Compare the descriptions with real examples and ask each other what fits. You do not need to reconcile every contradiction or accept a description that does not match your experience.
People also use compatibility frameworks to reflect on friendships, family relationships and collaboration. Keep the focus on observable behavior, communication and each person's boundaries.
A report that brings the methods together
An integrated report puts interpretations from several frameworks in one place. That can make comparison easier, while leaving the assumptions of each framework open to question.
Hour Light's Relationship User Manual organizes both people's chart interpretations into 20 chapters, including needs, communication and recurring friction. It provides discussion prompts for reading together.
A compatibility score should not decide whether you stay in a relationship. Use any reading alongside direct communication and your own experience of care, respect and safety.
See both charts together
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Frequently asked questions
What is the difference between synastry and Bazi compatibility?
Synastry is the Western astrology method of comparing two birth charts by overlaying one person's planets onto the other's, and it reads the chemistry between you: attraction, emotional fit, friction and the day-to-day feel of the bond. Bazi compatibility compares two Chinese Four Pillars charts and reads how your five elements interact, whether they support, balance or clash, which speaks more to long-term structure and timing. Synastry reads the spark, Bazi reads the foundation. They describe two different layers of the same relationship.
Is Bazi compatibility only about marriage?
No. Although it is often used for marriage matching, Bazi compatibility simply reads how two people's elemental energies interact, so it applies to any pairing: business partners, parent and child, close friends, family members and collaborators. Any two people whose energies meet regularly can be read this way. The question is not only romantic compatibility, but how two people support or strain each other in whatever role they share.
Does a low compatibility score mean we should not be together?
No. A compatibility reading is not a verdict and not a score that decides your relationship. Two charts that clash on paper often describe a couple who challenge and grow each other, while two that flow easily can describe comfort that drifts into routine. The value of a reading is awareness: it shows you where you naturally fit and where you will need patience, so you can meet those points with understanding instead of surprise. What you do with that is always your choice.
Do both people need their exact birth time for a compatibility reading?
For the most complete reading, both birth times help a great deal. Synastry needs each person's time to place the moon, rising sign and houses, and Bazi needs the hour to complete each person's four pillars. If one time is missing you can still read the parts that depend mainly on the date, such as sun-sign dynamics and each person's Bazi day master, while the time-sensitive layers stay approximate.
Can you read synastry and Bazi compatibility together in one report?
Yes. An integrated compatibility report computes both people's charts across many systems at once and reads them as one picture, so you see the chemistry layer and the structural layer side by side rather than juggling separate tools. Hour Light's Relationship User Manual crosses both birth charts through 37 systems, including synastry, Bazi compatibility and Zi Wei synastry, into a single 20-chapter relationship manual.