Synastry Compatibility Calculator
Sun-sign compatibility is only the surface. Synastry compares two full birth charts, and the deeper signals, the Moon, Venus, and Mars, often say more about how two people actually fit. Enter both sets of birth details to compare your placements. No signup, and everything runs in your browser.
Rising signs need accurate birth times. Without them, the Sun, Moon, Venus, and Mars comparison still holds, but treat the rising signs as approximate.
What Synastry Actually Compares
Where a simple compatibility check looks at two sun signs, synastry weighs the placements that shape a relationship most. The Moon shows how each person needs to feel safe and cared for, which often matters more day to day than the Sun. Venus shows how you love, and Mars shows how you pursue, so the cross-connection between them is the classic chemistry signal.
Why Two Clashing Sun Signs Can Still Work
Plenty of couples have sun signs that the books call incompatible while their Moons sit in the same element and their Venus and Mars line up beautifully. That is the whole point of looking past the sun sign. This calculator gives you the placements and an honest read on the element fit. It is a starting point for reflection, never a verdict on a real relationship.
The Honest Limit
A full synastry reading also weighs the exact angles between the two charts, which a quick element comparison cannot fully capture. Treat this as a thoughtful first look, not the final word. For where the evidence actually stands on astrology, see Is Astrology Real?
Frequently Asked Questions
- What is synastry?
- Synastry is the branch of astrology that compares two birth charts to see how two people interact. It looks at where each person's planets fall relative to the other's, rather than only comparing sun signs.
- Which placements matter most for compatibility?
- The Moon (emotional needs), Venus and Mars (how you love and pursue), and the Sun (core temperament) carry the most weight. Moon-to-Moon and Venus-to-Mars are the classic synastry signals, often more telling than sun signs alone.
- Do we need exact birth times?
- For the rising signs and houses, yes. The Sun, Moon, Venus, and Mars comparison still works without exact times, though the Moon can shift if a birth falls near a sign change.
- Is sun-sign compatibility enough?
- It is a starting point, not the whole story. Two people with clashing sun signs can have deeply harmonious Moons and a strong Venus-Mars connection, which is exactly what comparing the full placements reveals.
- Is this synastry calculator free?
- Yes, free and no signup. It runs in your browser from two sets of birth details. Timezone and historical daylight saving are handled automatically.
Next steps
- Want just the sun-sign read? Use the compatibility calculator.
- Curious about your own placements? Run your free birth chart.