Sidereal birth chart calculator

Put in your birthday to see your sidereal Sun sign straight away. Add your birth time and place and you go straight to your whole sidereal chart, with your Moon, rising sign and every other placement: it's free, it's drawn in 3D, and every planet is measured against the stars with the Lahiri ayanamsa.

What is a sidereal birth chart?

A sidereal birth chart measures each planet against the stars behind it (sidereal means "of the stars"). The sidereal zodiac anchors its twelve equal signs to the fixed stars: with the Lahiri ayanamsa, the bright star Spica sits on the line between Virgo and Libra. It's the zodiac of Vedic astrology (Jyotish), and some Western astrologers use it too.

The tropical zodiac, which most Western astrology and horoscopes use, ties the signs to the seasons instead: Aries always begins at the March equinox. The two zodiacs lined up around the year 285. Since then the equinox has drifted back through the stars by about 50 seconds of arc a year, one degree every 72 years, because the Earth's axis slowly wobbles. That gap is called the ayanamsa, and in 2026 it is 24.2 degrees.

It's the same sky either way. Your planets sit in exactly the same places; only the line where each sign starts moves. In the 3D sky on your chart page you can see it happen: switch to sidereal and the sign names slide about one sign along the stars while every planet stays put.

Why is my sidereal sign different?

Every placement moves back by the ayanamsa, about 24 degrees. A planet in the first 24 degrees of a tropical sign lands in the sign before it, and only one in the last 6 degrees stays in the same sign. So about four placements in five change sign, and most people find their Sun sign moves back one.

For example, a Sun at 10 degrees Aries in the tropical zodiac sits at about 16 degrees Pisces in the sidereal zodiac. A Sun at 28 degrees Aries stays in Aries, at about 4 degrees.

Sidereal sun sign dates

These are the days the Sun entered each sign in 2026, in Universal Time. The dates move by a day or so from year to year, so a birthday near a change needs the calculator above or your full chart.

Which ayanamsa do we use?

We use the Lahiri ayanamsa, also called Chitrapaksha. It's the standard in India: the Indian government's astronomical ephemeris uses it, and so do most Vedic astrologers and astrology apps. Our Lahiri matches the Swiss Ephemeris, the engine most astrology software runs on, to within a millionth of a degree, and the planets come from NASA JPL's DE440 ephemeris.

Other ayanamsas set the starting point a little differently. Fagan-Bradley's, used in Western sidereal astrology, is about 0.9 degrees larger than Lahiri's, Raman's about 1.4 degrees smaller and Krishnamurti's about 0.1 degrees smaller. So if another site disagrees with us, check which ayanamsa it uses: only a placement close to the start or end of a sign can change.

How to see your chart in sidereal

Put your birth details in the form at the top of this page and your chart opens in the sidereal zodiac. Any chart can switch, too: choose Sidereal in the line under its heading, where it says Tropical or Sidereal zodiac. Every placement, house cusp and aspect is worked out again, your highlights are read again, and we remember the choice for your next chart. You can switch back at any time.

Draw your sidereal chart

You can also see how the signs change for people you know: every celebrity birth chart on Pluto Garden lists the sidereal signs next to the tropical ones. For the 13th sign, see Ophiuchus: even the sidereal zodiac keeps twelve equal signs.

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