About & Method

Birth Chart Atlas is an independent astrology website with free tools and guides for curious people. Everything here is meant for entertainment, reflection and fun.

Where the content comes from

The zodiac sign profiles and compatibility readings are original writing. Compatibility scores are generated from traditional astrological relationships between signs: how far apart they sit on the zodiac wheel, and how their elements and modalities interact. They are a guide for conversation, not a prediction.

How the calculator works

• Zodiac: the tropical zodiac, as used by most Western astrologers.
• Sun and Moon: positions are computed from published astronomical series (Jean Meeus, Astronomical Algorithms) and match a professional ephemeris to within about 0.02 degrees in our testing.
• Rising sign: computed from the local sidereal time, your latitude and the obliquity of the ecliptic. It is sensitive to birth time, so a few minutes' difference can matter near a sign boundary.
• Time zones: your birth city's historical time zone rules are applied through your browser's built-in time zone database.
• Places: city names, coordinates and time zones come from GeoNames, licensed under CC BY 4.0.

Privacy by design

All calculations happen in your browser. We do not receive, store or log the birth details you enter.

Mercury retrograde dates

Retrograde and direct stations were computed astronomically and are shown in UTC.

Questions or corrections

Spotted something wrong? Get in touch.