Pick two signs to see how their elements and temperaments tend to play off each other.
Person A
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Person B
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The Quick mode compares two sun signs by their element — Fire, Earth, Air, or Water — the foundation classical Western astrology uses for compatibility. Fire and Air traditionally energize each other, Earth and Water traditionally nurture each other, same elements tend toward instant mutual recognition, and the remaining combinations bring more friction, which can mean real growth or real difficulty depending on the people involved.
The Full mode goes a real step further: using exact birth date, time, and location for both people, it calculates each person's actual Sun, Moon, and Rising signs — the same math behind the Birth Chart Calculator — and compares three separate relationships: Sun to Sun (core identity), Moon to Moon (emotional rhythm), and each person's Sun to the other's Moon (how your core self lands on their emotional world, and vice versa). That's a meaningfully fuller picture than sun signs alone.
To be direct about what it still isn't: this is not full professional synastry. A complete synastry reading also weighs Venus, Mars, and the other planets, along with specific angular relationships between two entire charts — placements this tool doesn't calculate. Both modes here are a starting point for reflection, not a verdict. Read more in Synastry: How Relationship Astrology Actually Works.