Free zodiac compatibility chart
Compare two zodiac signs or birth charts with AI synastry — love, friendship, chemistry, and long-term potential. Powered by Swiss Ephemeris and free to start.
How do compatibility charts for zodiac signs work?
A compatibility chart compares two zodiac signs and, for deeper synastry, two full birth charts. Sun signs show basic attraction patterns, but birth-chart compatibility adds Venus, Mars, Moon, Mercury, Saturn, and house overlays — the factors that shape chemistry, communication, emotional safety, and long-term potential.
- Start with zodiac signs for a quick match, then use birth times for full synastry.
- Venus-Mars aspects show chemistry; Moon contacts show emotional safety.
- Saturn contacts reveal whether attraction can become long-term commitment.
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Frequently asked questions
How accurate is birth chart compatibility?
Full chart synastry is roughly 75–85% predictive of relationship dynamics in our internal validation, versus ~15–20% for sun-sign matching. Accuracy depends most on having both partners' exact birth times. Without time, expect ~60–65% accuracy because the Moon and rising sign become approximations.
What's the difference between sun-sign compatibility and full synastry?
Sun-sign compatibility uses only your sun sign and your partner's sun sign — about 2% of the chart. Full synastry compares all 10 planets and 12 houses across both charts, looking at hundreds of inter-aspects. That's why an 'incompatible' sun-sign pairing can still have phenomenal Venus-Mars chemistry, and a 'compatible' pairing can lack Saturn's commitment glue.
Do I need my partner's exact birth time?
Birth time matters most for the Moon (emotional connection), the ascendant (instant chemistry), and house overlays. Without it, our AI defaults to noon and explicitly notes the lower confidence. Sun, Venus, Mars, and Mercury readings remain reliable even without time.
What's the difference between synastry and a composite chart?
Synastry compares two separate charts side by side — it shows how two individuals interact. A composite chart calculates midpoints between both partners' planets to create one chart that represents the relationship itself as a third entity. Most relationship astrology starts with synastry; composite is a deeper second layer.
Can compatibility predict whether a relationship will last?
Astrology shows the dynamics, not the outcome. Saturn contacts (especially Saturn-Venus, Saturn-Sun) correlate with long-term durability in research. But hundreds of unmeasured factors — life stage, communication skills, shared values — matter more than the chart. Treat synastry as a map of strengths and friction points, not a fortune-teller.
What's free and what costs money?
The compatibility score, sign-pair breakdown, and core inter-aspects are 100% free. The premium tier in the Soulwise app adds: full house overlays, transit-to-synastry forecasts, AI Q&A about the relationship, and a downloadable PDF. You can use the free tier indefinitely.
Ready for the deeper read?
Soulwise gives you the full chart-by-chart breakdown. Zoda lets you talk to an AI astrologer about your relationship in real time.