How do I read a synastry chart?

Start by looking at aspects between the Big Three (Sun, Moon, Rising), then check Venus-Mars for attraction, Mercury for communication, and Saturn for longevity. Focus on patterns rather than individual aspects.

Do I need birth times for synastry?

Birth times are helpful but not required. Without birth times, you can still analyze planetary aspects. With birth times, you also get house overlays and Ascendant/Midheaven aspects for deeper analysis.

What are the best synastry aspects for love?

Venus-Mars aspects indicate attraction, Sun-Moon aspects show emotional compatibility, and Venus-Venus contacts represent shared values. Saturn aspects, while sometimes challenging, often indicate lasting relationships.

Free Synastry Chart Calculator - Relationship Astrology Compatibility

What You'll Discover

Comprehensive insights into your relationship through synastry analysis

Compatibility Score

Get an overall compatibility percentage plus detailed breakdowns for passion, communication, stability, emotional connection, and growth.

Key Aspects

See all the planetary aspects between your charts, from harmonious trines to challenging squares, with interpretations.

House Overlays

Discover where your partner's planets fall in your houses, revealing how they influence different areas of your life.

Strengths & Challenges

Identify your relationship's natural gifts and potential friction points with actionable advice.

Works Without Birth Time

Get valuable insights even without exact birth times. Add times later for house overlays and deeper analysis.

Private & Secure

Your birth data is only stored if you choose to save your report. Calculate as many charts as you like.

What Is a Synastry Chart?

A synastry chart is a relationship astrology chart that compares two birth charts to show how two people naturally connect — where you feel ease, attraction, growth, and where friction can show up. If you're searching for "birth chart synastry" or "natal chart synastry," you're in the right place: it's the same idea, just different wording. Synastry works by overlaying Person A's planets and angles with Person B's planets and angles, then analyzing the contacts (aspects) between them. These contacts describe the chemistry (like Venus–Mars), emotional fit (Sun–Moon), communication style (Mercury), and long-term glue or lessons (Saturn). Unlike a composite chart (which creates a single chart for the relationship), synastry keeps both individuals separate, showing exactly how each person affects the other. This makes it ideal for understanding day-to-day dynamics, attraction patterns, and areas of natural harmony or tension.

How to Read a Synastry Chart (Quick 6-Step Checklist)

Follow these steps to understand your synastry chart

1

Start with the Big 3

Look at Sun, Moon, and Ascendant connections for overall vibe and emotional fit. These are the foundation of compatibility.

2

Check Venus & Mars

These planets reveal attraction, affection style, and how desire shows up between you. Key for romantic relationships.

3

Look at Mercury Contacts

Communication flow, potential misunderstandings, and mental chemistry are shown through Mercury aspects.

4

Identify Saturn Links

Saturn reveals commitment potential, responsibilities, and repeating lessons in your relationship.

5

Notice Nodes & Angles

If birth times are known, the Nodes and angles show the 'fated' feeling, timing, and major life impact.

6

Review Patterns

Don't focus on single aspects. Clusters of similar aspects tell the real story of your relationship.

Key Synastry Aspects Explained

Understanding the most important planetary connections in relationship astrology

Understanding House Overlays

House overlays show where your partner's planets fall in your birth chart houses. This reveals how they activate different areas of your life and which topics naturally come up in your relationship. For example, if your partner's Sun falls in your 7th house, they light up your partnership sector — you may naturally see them as a significant partner. If their Venus lands in your 2nd house, they might influence your values, finances, or self-worth. Key houses for romantic relationships: • 1st House: They affect your identity and how you see yourself • 5th House: Romance, creativity, fun, and children • 7th House: Committed partnership, marriage, balance • 8th House: Intimacy, shared resources, transformation House overlays require accurate birth times for both people. Without birth times, we can still analyze aspects between planets, but the house information won't be available.

Synastry vs Composite Chart

Understanding the difference between these two relationship chart types

Synastry compares two individuals: it answers 'how do we affect each other?' A composite chart blends two charts into a single relationship chart: it answers 'what is the relationship itself like as a third entity?' **Use Synastry when you want to know:** • How you affect each other day-to-day • Areas of natural attraction and chemistry • Communication patterns between you • Where friction or misunderstandings arise • How each person experiences the other **Use Composite when you want to know:** • The relationship's overall purpose • How the relationship appears to others • The relationship's strengths as a unit • How the relationship evolves over time • Major themes and challenges you face together Most astrologers recommend starting with synastry for compatibility and day-to-day dynamics, then using composite to understand the relationship as its own entity.

Synastry by Relationship Type

How to interpret synastry for different kinds of relationships

Romantic Relationships

For romantic synastry, focus first on Venus-Mars aspects (physical attraction), Sun-Moon aspects (emotional fit), and 5th/7th house overlays (romance and partnership). Look for a mix of harmonious aspects (trines, sextiles) for ease, and some tension (squares) for passion. Too many easy aspects can lack spark; too many hard aspects can exhaust. Saturn aspects indicate staying power — not always romantic, but often present in long-term relationships.

Friendship Compatibility

Friendship synastry emphasizes Mercury (communication) and 11th house overlays (friendship, shared goals). Sun and Moon contacts show whether you 'get' each other on a basic level. Jupiter contacts are wonderful for friendships — they bring expansion, generosity, and good times. Uranus contacts suggest an exciting, unconventional friendship. Look at Saturn for friendships that stand the test of time.

Business Partnerships

For business synastry, focus on Mercury (communication), Saturn (reliability, structure), and 2nd/10th house overlays (money, career). Mars aspects show how you take action together — harmonious Mars can be productive; challenging Mars may create competition or conflict. Jupiter-Venus contacts can indicate financial benefit through the partnership.

Family Relationships

Family synastry often shows strong Moon contacts (emotional patterns passed down), Saturn aspects (responsibilities, lessons), and 4th house overlays (home, family roots). Pluto aspects in family synastry can indicate power dynamics, control issues, or deep transformation through the relationship. Node contacts often appear in significant family relationships, suggesting karmic connections.