Two birth dates · private calculation
Birth Chart Compatibility
Compare two birth dates and read what runs between you two—how you love, how you argue, and what holds you together. Astrologers call this synastry: laying two birth charts side by side. Free, and your data never leaves your browser.
You two
Your compatibility
For astrologers: exact aspects, orbs, houses, and antiscia
Planet contacts by dimension
Exact aspects between the bodies of both people—1 marks person one, 2 person two. An empty dimension means no tight contact within the allowed orbs, not a missing theme.
What this result can't know
Frequently asked questions
Birth chart compatibility in short
What the comparison shows, why the birth time and place help, and how privacy and prediction are handled.
What is birth chart compatibility?
A comparison of two births: from the dates we determine both Sun signs and the bond type they form on the zodiac circle. Add a time and place and exact angles between the Moon, Mercury, Venus, Mars, and Saturn join in, with house overlays on top. It is a symbolic profile of two charts, not a grade and not a prediction of the relationship.
What is synastry?
The astrological technique behind this calculator: two birth charts laid side by side and read through the angles—aspects—that one person's planets make to the other's. Astrologers have used it for centuries to describe how two people meet in feeling, conversation, drive, and commitment. This page runs it on exact ephemerides.
Why does the time of birth matter?
The Sun sign usually follows from the date alone; only on a day when the Sun changes signs does the hour decide, and the calculator then offers both options. The Moon is the real reason: it crosses a sign in about two and a half days, so a date alone leaves it uncertain. Even a rough part of the day—a six-hour window—narrows the Moon from about fourteen degrees to under four.
Why the birthplace?
The place fixes the horizon—from it we compute the ascendant, midheaven, and houses of both people, plus the chart overlays: in which houses of one person the other's planets land. Planetary positions do not need a place, so it stays optional; without it the result simply leaves those axes out. The place helps only together with an exact time.
Is this a prediction of the relationship?
No. The result describes the geometry of two Sun signs and the actual positions of the planets, not the quality or the future of a specific relationship. A trine is not a verdict of success and a tense angle is not a sentence—they are symbols a couple can work with deliberately.