Free Sidereal Birth Chart Calculator

What a sidereal birth chart is

A sidereal birth chart maps the sky against the fixed stars, which is where the word comes from: sidus, Latin for star. Your grahas are placed by where they actually sat among the constellations at the moment you were born, not by where the seasons were.

That's the zodiac Indian astrology has used for a couple of thousand years, so a sidereal chart and a Vedic kundali are the same object under two names. Jyotish, Vedic astrology, sidereal astrology: the labels differ by tradition and by continent, and the underlying chart doesn't.

Why your sidereal sign is usually one sign back

Because the two zodiacs have drifted apart. Tropical astrology fixes 0 degrees Aries to the spring equinox, and the equinox itself creeps backwards through the constellations at roughly one degree every 72 years. Sidereal astrology keeps 0 degrees Aries pinned to the stars instead.

In 2026 the gap is about 24 degrees and 13 minutes. That's most of a sign, which is why a Sun at 12 degrees tropical Leo lands at 17 degrees sidereal Cancer. Most people move back one sign. Anyone born in roughly the last six days of a tropical sign usually doesn't move at all.

Here's the thing: nothing about the sky changed. Only the ruler being held up against it did.

Sidereal or tropical: is one of them wrong?

Neither is wrong, and treating this as a contest is the fastest way to misunderstand both. They're two conventions for measuring the same positions, and each has a body of practice built on top of it that assumes its own measurement.

What matters is that you can't mix them. Nakshatras, Vimshottari dasha, mangal dosha and guna milan were all worked out on sidereal positions, so feeding them a tropical chart produces answers that look plausible and are quietly wrong by nearly a sign. If you're reading Indian astrology, you want the sidereal chart. If you're reading a Western transit report, you want the tropical one.

Which ayanamsa this calculator uses, and why it matters

This page uses Lahiri, which is the ayanamsa the Indian government's calendar reform committee settled on and the one almost all Indian astrologers work with. The ayanamsa is just the size of that gap between the two zodiacs, and different schools measure it slightly differently.

The disagreements are small but they aren't nothing. Raman and Krishnamurti sit within about a degree of Lahiri, and a degree is enough to move a planet sitting near a boundary into the next nakshatra, which changes the pada and can shift a dasha start date by months. So when a chart you got elsewhere disagrees with this one by a fraction of a degree, the ayanamsa is usually the reason rather than a mistake by either side.

How this sidereal chart is calculated

Every position on this page comes from the Swiss Ephemeris, the same high-precision astronomical library professional astrology software is built on. Positions are computed for your exact timestamp and coordinates, then the Lahiri ayanamsa is subtracted to give sidereal longitudes. Nothing is rounded to a sign and nothing is looked up in a table.

No part of that calculation is done by AI, and it's worth being precise about why that distinction matters: astronomy is deterministic, so a calculation either is right or isn't, and the Swiss Ephemeris is how you make sure it is. AI is used on this site only to write interpretations of a chart that has already been computed.

• Sidereal zodiac with Lahiri (Chitrapaksha) ayanamsa, the standard used for Indian panchangs.
• Whole-sign houses: the lagna sign is the first house, the next sign the second, and so on.
• Mean Rahu and Ketu, which are always retrograde.
• Your local birth time is converted to UTC using the historical timezone of the birth place.
• Vimshottari dasha of 120 years, started from the Moon's exact position in its nakshatra.

Reading the chart you get back

Start with three values, because they carry most of the weight. The rising sign (lagna) is the sign that was climbing over the eastern horizon at your birth, and it sets the whole house layout. The Moon sign (rashi) is what Indian horoscope columns are actually written for, which surprises people who expect their Sun sign. The nakshatra is the lunar mansion the Moon occupied, and it decides where your dasha sequence starts.

Most people don't realise the rashi and the lagna are different things, and that's usually the first question after a chart appears. Under the chart you'll find a table with each graha's exact degree, its nakshatra and its pada, so you can check this against any kundali you already have rather than take it on trust.

Why the birth time matters more than people expect

The rising sign moves about one degree every four minutes, so it changes sign roughly every two hours. A birth time that's out by fifteen minutes can leave every house in the chart correct or shift the lot, depending on how close you were born to a boundary.

Use the time on a birth certificate or hospital record if you can get it. The Moon is far more forgiving, at about 13 degrees a day, so your Moon sign and usually your nakshatra survive an approximate time even when the houses don't. Place matters too, though less than people fear: picking a city 50 to 100 km from your actual town moves the rising sign by well under a degree.

What a sidereal chart won't tell you

It won't tell you what will happen. A sidereal birth chart is a record of positions and the periods that follow from them, and the reading built on top of it is interpretation within a tradition, which is a different kind of claim from the astronomy underneath.

Traditions also disagree with each other on real points, including which ayanamsa is correct and how much weight a divisional chart deserves, and anyone telling you those questions are settled is overselling. What you can rely on here is the arithmetic. Calculate your free Vedic astrology chart above, download the PDF if you want it on paper, or have the reading written if you'd rather someone walked you through what the placements mean.