What is a 13 sign birth chart?

A 13-sign birth chart uses the astronomical positions of planets through actual constellations, including Ophiuchus (the Serpent Bearer) between Scorpius and Sagittarius. This differs from the tropical 12-sign system which is fixed to seasons rather than stars.

Is this calculator accurate?

Yes, our calculator uses NASA JPL DE421 ephemeris data and IAU constellation boundaries. The positions shown match where planets actually appear among the stars at your time and place of birth.

Why is my sun sign different from my tropical sign?

Due to Earth's axial precession over 2000+ years, tropical signs have drifted about 24 degrees from their constellation namesakes. Our sidereal chart shows where the Sun actually was among the stars, which is typically one sign earlier than tropical astrology indicates.

Natal Chart

Discover your 13-sign sidereal birth chart, aligned with the true sky rather than tropical astrology. Enter your birth information and click Calculate Chart to reveal your TRUE SUN SIGN and the exact positions of the stars and planets at the moment you were born. Once calculated, you can download a PDF of your chart and explore the sky the day you were born.

Birth Date & Time

Date

Time (12h or 24h)

I don't know my birth time

Timezone

Birth Location

Planetary Placements

Planet	Sign	Degree	House	Element

Celestial Modules

Natal Chart

Birth Date & Time

Birth Location

Planetary Placements

Element & Modality Balance

Elements

Modalities

Aspect Grid

Celestial Modules

Natal Chart

Birth Date & Time

Birth Location

Planetary Placements

Element & Modality Balance

Elements

Modalities

Aspect Grid

Location Settings