Your Sign in Both Systems: Tropical and Sidereal

Two zodiacs, one sky

Both systems divide the ecliptic, the Sun’s yearly path, into twelve signs of 30 degrees. They differ in where they start counting.

• The tropical zodiac of Western astrology starts at the March equinox, so 0 degrees of Aries is fixed to the seasons.
• The sidereal zodiac of Vedic astrology starts from a point fixed against the stars. The most common choice in India is the Lahiri ayanamsa, used by the Indian government’s calendar authorities.

Two thousand years ago the zodiacs coincided. Since then the Earth’s axis has slowly wobbled, so the equinox has moved backwards against the stars, about one degree every 72 years. Today the gap is about 24 degrees.

What that means for your sign

A sign is 30 degrees wide, so a gap of about 24 degrees moves most people one sign back. For roughly four in five birthdays the Sun sign differs between the systems, and the same is true of the Moon and the Rising sign. If the Sun is in the last six degrees of a tropical sign, it usually stays in the same sign in the sidereal zodiac.

Is one of them right?

No. They answer different questions. The tropical zodiac describes the seasonal cycle as it is experienced from Earth, and the sidereal zodiac describes positions against the fixed stars. Each has centuries of practice and its own methods of interpretation, and mixing the two (reading a tropical sign with Vedic rules, or the reverse) is what causes confusion. The two sister sites keep them separate.

Using the result

After your result, the tool links each sidereal placement to the matching page on the Vedic site, which reads it in the Vedic way. Those pages call the Moon sign the rashi and the Rising sign the lagna. For a longer explanation, read Moon sign versus Sun sign on the Vedic site.

Frequently asked questions