Synastry Chart Calculator
Free synastry chart calculator: compare two birth charts and see every aspect between them, with exact orbs, in seconds.
Current planets
…💡Tips for Best Results
- •Use exact birth times for the most accurate results. If unknown, use 12:00 PM.
- •Select the birth city to automatically fill coordinates and timezone.
- •Try our sample data to see how the calculator works.
What is a Synastry Chart?
🌟Understanding Synastry Chart Meaning
A synastry chart is a powerful astrological tool that compares two birth charts to analyze relationship compatibility. Unlike a single birth chart that reveals your individual personality, a synastry chart shows how two people interact, connect, and influence each other on cosmic levels.
How It Differs from Individual Charts
What Can You Discover?
Romantic Relationships
A birth chart synastry report reveals romantic compatibility, attraction patterns, and long-term potential
Friendship Compatibility
Understand why you click with certain friends through synastry birth charts analysis
Business Partnerships
Evaluate working relationships and team dynamics using chart synastry
Family Dynamics
Gain insights into parent-child or sibling relationships through astrological comparison
💡 Pro Tip: The most accurate synastry chart requires exact birth times for both individuals. Our free calculator uses a NASA-grade ephemeris (astronomy-engine, accurate to well under one arcminute) for professional-quality results.
Understanding Planetary Aspects in Synastry
Planetary aspects reveal how two people's energies interact. Each aspect creates a unique dynamic—from harmonious flow to challenging tension—shaping relationship compatibility.
Conjunction
0°When two planets occupy the same zodiac degree, their energies merge completely. This creates powerful chemistry and deep understanding, though it can feel overwhelming at times.
GOOD FOR:
💡 Sun conjunct Moon creates an instinctive understanding between partners—you just 'get' each other.
Trine
120°Planets 120° apart create effortless harmony. This is the 'easy love' aspect where things flow naturally without effort. Perfect for long-term compatibility.
GOOD FOR:
💡 Venus trine Mars brings natural attraction and balanced give-and-take in romance.
Sextile
60°At 60°, sextiles create opportunities for growth and cooperation. Less intense than trines but equally beneficial, offering chances to develop the relationship actively.
GOOD FOR:
💡 Mercury sextile Mercury means you think alike but keep conversations interesting.
Opposition
180°Planets 180° apart create magnetic attraction with inherent differences. This aspect brings both fascination and friction—the classic 'opposites attract' dynamic.
GOOD FOR:
💡 Sun opposition Moon creates magnetic pull—you're different but complete each other.
Square
90°The 90° square creates friction and challenges that force growth. While difficult, these aspects add passion and motivation to overcome obstacles together.
GOOD FOR:
💡 Venus square Mars creates sexual tension—challenging but intensely passionate.
Quincunx
150°At 150°, quincunx aspects require constant adjustment and compromise. These relationships teach flexibility and adaptation, though they can feel awkward initially.
GOOD FOR:
💡 Moon quincunx Venus means emotional and affection styles differ—requires conscious effort.
Key Planetary Connections to Look For
Sun-Moon
CriticalThe Sun-Moon connection reveals core compatibility between your essential self (Sun) and emotional needs (Moon). Harmonious aspects here indicate deep mutual understanding.
Venus-Mars
RomanticVenus-Mars aspects determine romantic and sexual chemistry. These combinations show how attraction, affection, and desire play out between partners.
Moon-Moon
EmotionalMoon-to-Moon aspects reveal emotional compatibility and how well you nurture each other. Essential for long-term domestic harmony and family life.
Mercury-Mercury
CommunicationMercury connections determine how well you communicate and understand each other's thinking. Crucial for intellectual compatibility and resolving conflicts.
Use the free synastry chart calculator above to discover the planetary aspects between you and your partner.
How to Read a Synastry Chart in 5 Steps
A synastry chart places two birth charts on one wheel and draws lines — aspects — between the planets of one person and the planets of the other. A full chart can show forty or more of them, which is where most people get lost. Professional astrologers do not read every line with equal weight; they read in a fixed order. Here is that order.
Start with the personal planets, not the outer ones
Sun, Moon, Mercury, Venus and Mars change sign every few weeks at most, so their positions are genuinely personal. Jupiter, Saturn, Uranus, Neptune and Pluto move so slowly that everyone born within a few years shares the same sign — an aspect from your Pluto to your partner's Sun says more about your generation than about the two of you. Read personal-to-personal aspects first, personal-to-outer second, and treat outer-to-outer aspects as background.
Rank the aspects by orb, not by name
The orb is how far an aspect is from exact. A Venus–Mars trine at 0.5° is felt every day; the same trine at 7° is faint. A rough scale: under 2° is dominant, 2–5° is clearly present, above 5° is a whisper. Our free synastry chart calculator prints the orb beside every aspect — sort by the tightest first and you will usually find the two or three lines that define the relationship.
Check the house overlays
Where your partner's planets fall in your houses shows which part of your life they switch on. Their Sun in your 7th house feels like a partner; in your 10th house they push your career; their Moon in your 4th house makes them feel like home. Overlays depend on an accurate Ascendant, so they need both birth times — if one is unknown, skip this step rather than guess.
Count the balance, then look for the theme
Tally the harmonious aspects (trines, sextiles, most conjunctions) against the challenging ones (squares, oppositions). No real relationship scores 100% on either side: a chart made only of easy aspects often lacks drive, and one made only of hard aspects burns out. Then look for repetition. If three separate aspects all involve Mercury, the relationship's story is about communication, whatever the other lines say.
Look for two-way ("double whammy") aspects
The strongest signature in any synastry chart is a mutual aspect: your Moon aspects their Venus and their Moon aspects your Venus. Both people feel the connection the same way, which is why astrologers call it a double whammy. A one-way aspect is real but lopsided — one person feels it more than the other, and that imbalance is often the answer to "why does this feel unequal?"
Once you have these five layers you have a reading, not a list. For a deeper look at any single line, every major pairing has its own page in our synastry aspects library.
Free Synastry Chart vs. Paid Synastry Report
The synastry chart calculator above is completely free and is enough for most people who want to check one relationship. You get the full bi-wheel, the five personal planets for both people, every aspect between them with its exact orb, house overlays when both birth times are known, compatibility scores, and a shareable link that never expires.
A paid synastry report is for when the free chart raises questions the summary cannot answer. Pro adds the outer planets plus Chiron, Lilith and the lunar nodes, over 270 written interpretations, an AI-generated narrative, and PDF export. The one-time Deep Synastry Report goes further: a verdict-first reading of one couple, a dated look at the year ahead, and a concrete action list — for people who already know the relationship matters and want to know what to do with it.
| Feature | Free synastry chart | Pro | Deep Report |
|---|---|---|---|
| Bi-wheel + all aspects with orbs | |||
| Personal planets (Sun–Mars) | |||
| Jupiter–Pluto, Chiron, Lilith, Nodes | |||
| Written interpretations | Summary | 270+ | Full narrative |
| Year-ahead timing + action list | |||
| Price | $0 | $14.99/mo | $39 once |
If you only want to know whether two charts click, stop at the free chart — it is the same calculation either way.
Frequently Asked Questions About Synastry Charts
Everything you need to know about chart synastry and relationship compatibility analysis
Ready to Explore Your Synastry Chart?
Get your free, detailed birth chart synastry report in seconds. No signup required, 100% free, instant results.