Enter two birth moments and see how the two real skies meet — each Sun, Moon and rising sign, the aspects your planets make to each other, and the blend of your elements. A true synastry, drawn to the arc-minute. Free.
Synastry is the branch of astrology that reads two charts together. It doesn't reduce two people to their Sun signs — the "are a Leo and a Scorpio compatible?" question a magazine asks. It lays one whole natal chart over the other and looks at the real geometry between them: where one person's Moon meets the other's Venus, whether their Suns support or challenge each other, how their Mars energies fall. Those cross-aspects are the actual grammar of astrological compatibility.
This free calculator casts both natal charts from a true ephemeris and shows you all of it: each person's Sun, Moon and rising sign, the aspects your planets make across the two charts, and the element blend between you — the same figures an astrologer would draw by hand.
Your Sun sign is one body out of ten. Two people with "incompatible" Sun signs can have a Moon-trine-Moon and a Venus-conjunct-Mars that make the whole thing sing; two "compatible" Suns can miss each other entirely everywhere else. Real compatibility is read across the whole chart, which is exactly what a synastry does — and why it needs both birth charts, not two star signs.
Without a birth time, a person's rising sign and any Ascendant aspects can't be fixed — the sky turns a full degree every four minutes. Everything else (each Sun, Moon and planet by sign, and the aspects between them) stays exact. If you don't know a time, a chart cast at noon still gives a true and useful synastry.
New to any of this? The guide explains it in plain language: how zodiac compatibility actually works, what a natal chart is, the planets, and the elements. Or cast a single free birth chart first.
A synastry maps a meeting. To have one whole sky read — line by line, in words — is The Book of You: a personalized keepsake written from one person's exact placements, in the voice of an old sky-scribe.
Have your chart read → or gift someone their own book ✦Yes. Enter two birth moments and your full synastry — each Sun, Moon and rising, the cross-aspects and the element blend — appears at once, computed to the arc-minute, at no cost and with no account. The written reading of what it all means is the one thing we sell.
They help but aren't required. A birth time sets that person's rising sign and any aspects to their Ascendant. Leave one blank and we cast that chart at noon — every Sun, Moon and planet by sign, and the aspects between the two charts, stay exact.
A synastry is two natal charts read together — one person's planets measured against the other's — to see the aspects, or geometric relationships, that form between them. It is how astrology actually reads compatibility, beyond Sun signs.
No. Synastry reads the connection between any two people — partners, friends, a parent and child, collaborators. The chart shows how two skies meet; what kind of bond it is, is up to you.