Sidereal vs Tropical: Why Your Vedic Sign Is Different, and Which Zodiac to Use

What is the difference between the sidereal and tropical zodiac?

The tropical zodiac begins Aries at the March equinox, so its signs follow the seasons. The sidereal zodiac begins Aries at a fixed point among the stars, so its signs follow the constellations. Because the equinox slowly slides backward against the stars, the two now sit about 24 degrees apart, almost a whole sign.

Everything else is the same. Both zodiacs divide the Sun's yearly path into twelve equal signs of 30 degrees, with the same names, the same order and the same ruling planets. The only question is where you put zero. Western astrology, including the readings on this site, uses the tropical zodiac. Indian astrology, often called Vedic astrology or Jyotish, uses the sidereal one, as do a small number of Western astrologers.

The same twelve signs, started from two different points. The sidereal signs begin about 24 degrees later, so most positions land in the sign before.

Neither zodiac is a measuring mistake. A planet at a given point in the sky is at that point in both systems. The tropical label tells you where it stands in the year's cycle of seasons; the sidereal label tells you which part of the starry background it stands against. They are two coordinate systems for one sky.

Why is my Vedic sign different from my Western sign?

Because the sidereal signs start about 24 degrees later. If your Sun sits in the first 24 degrees of a tropical sign, a Vedic chart puts it in the sign before. That covers about four birthdays in five, so most people who are Virgo in Western astrology are Leo in a Vedic chart.

Only the last six degrees or so of each tropical sign keep the same name in both systems, and the Sun crosses six degrees in about six days. Born on September 1? Virgo in Western astrology, Leo in a Vedic chart. Born on September 20? Virgo in both. Over 2026, the Sun's two signs differ about 81% of the time.

The same shift applies to everything else in the chart: the Moon, the rising sign and every planet move back by the same 24 degrees. Most of them change sign, some don't, and that is why a Vedic chart of the same birth can look like a reshuffled version of the Western one. It isn't a different sky. It is the same positions with different names on them.

What is my sidereal sign?

Your sidereal sign is your tropical position minus the ayanamsa, which is about 23 to 24 degrees for anyone born since 1950. Enter your birth date below. The finder shows your Sun in both zodiacs, and tells you when the answer depends on your birth time because the Sun changed sign that day.

Your Sun sign, tropical and sidereal

Birth date

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YearYear2026202520242023202220212020201920182017201620152014201320122011201020092008200720062005200420032002200120001999199819971996199519941993199219911990198919881987198619851984198319821981198019791978197719761975197419731972197119701969196819671966196519641963196219611960195919581957195619551954195319521951195019491948194719461945194419431942194119401939193819371936193519341933193219311930192919281927192619251924192319221921192019191918191719161915191419131912191119101909190819071906190519041903190219011900

Where you were bornSomewhere else, or not sureUS Pacific (Los Angeles, San Diego, Seattle)US Mountain (Denver)ArizonaUS Central (Chicago, Dallas)US Eastern (New York, Miami)AlaskaHawaiiCanada: VancouverCanada: Toronto, MontrealCanada: HalifaxPuerto RicoMexico: TijuanaMexico: Mexico CityBrazil: São Paulo, Rio de JaneiroArgentina: Buenos AiresUKIrelandPortugal (mainland)Spain (mainland)FranceGermanyItalyNetherlandsPolandGreeceUkraine (Kyiv)Russia: MoscowTurkeyIsraelLebanonUnited Arab EmiratesIndiaPhilippinesChinaJapanAustralia: Sydney, Melbourne, CanberraAustralia: Brisbane (Queensland)Australia: AdelaideAustralia: PerthNew ZealandSouth AfricaNigeriaUTC-12UTC-11UTC-10UTC-9:30UTC-9UTC-8UTC-7UTC-6UTC-5UTC-4UTC-3:30UTC-3UTC-2UTC-1UTC+0UTC+0:20 (Netherlands before May 1940)UTC+1UTC+1:20 (Netherlands before May 1940, summer)UTC+2UTC+3UTC+3:30UTC+4UTC+4:30UTC+5UTC+5:30UTC+5:45UTC+6UTC+6:30UTC+7UTC+8UTC+9UTC+9:30UTC+10UTC+10:30UTC+11UTC+12UTC+12:45UTC+13UTC+14

Birth time (optional)

Show both signs

Covers births from 1920 to 2026, with the Lahiri ayanamsa. The calculation runs in your browser and your birth details stay there. The site keeps only an anonymous count of tool use, with a short result such as the sign found.

A Vedic astrologer will usually lead with your Moon sign and your rising sign rather than your Sun. Both need more than a date: the Moon moves about 13 degrees a day and the rising sign changes every two hours or so. The rule is the same for them, though: take the tropical position and count back by the ayanamsa.

What is an ayanamsa?

The ayanamsa is the distance between the two zodiacs: how far the equinox has drifted from the sidereal starting point. In the Lahiri ayanamsa, the one most Indian astrologers use, it is about 24°14′ in 2026, and it grows by about one degree every 72 years. Subtract it from a tropical position to get the sidereal one.

The Lahiri ayanamsa is named after N. C. Lahiri, member secretary of India's Calendar Reform Committee of 1952 to 1955 (Positional Astronomy Centre, Kolkata). It fixes the sidereal zodiac so that the bright star Spica, called Chitra in India, was meant to sit at the start of Libra, and it is by far the most widely used system in India (Wikipedia, "Ayanamsa"). The value set in 1956 was 23°15′ for March 21 of that year.

Other schools use slightly different starting points. The Fagan-Bradley ayanamsa, used by Western sidereal astrologers, runs about 53 minutes of arc ahead of Lahiri, and other Indian systems such as Raman's and Krishnamurti's differ too (Swiss Ephemeris, ayanamsha definitions). Raman's, for example, runs about a degree and a half behind Lahiri. So two Vedic programs can disagree by up to about a degree and a half, and for a planet near the edge of a sign, that changes the sign.

Why do the tropical and sidereal zodiacs drift apart?

Because of precession. The Earth's axis wobbles like a spinning top, one full turn in about 25,772 years, so the March equinox slides backward along the stars by about 50.3 seconds of arc a year: one degree every 72 years. The tropical zodiac moves with the equinox; the sidereal zodiac stays with the stars.

The wobble comes from the pull of the Sun and the Moon on the bulge around the Earth's equator. The Greek astronomer Hipparchus found the drift in the second century BC. Comparing his own star positions with those recorded by Timocharis more than a century earlier, he saw that the star Spica had shifted about two degrees against the autumnal equinox (Wikipedia, "Axial precession"). The rate he estimated was at least one degree per century; the modern figure is one degree in about 71.6 years. The same slow drift carries every fixed star through the signs: see where the fixed stars sit now.

By the Lahiri count, the two zodiacs started from the same point around the year 285 AD, and they have been separating ever since. The March equinox now falls at about 6 degrees of sidereal Pisces. The same slow drift is behind talk of an Age of Aquarius: by the Lahiri count, the equinox will move from sidereal Pisces into Aquarius in a little over four hundred years, and by the constellation boundaries astronomers use, it crosses into Aquarius around the year 2600 (Wikipedia, "Age of Aquarius").

Which zodiac did the ancient astrologers use?

Both, and the record is mixed. The Babylonians fixed their signs to the stars. Greek astronomers measured from the equinoxes, and in the second century Ptolemy argued firmly for that, while some of his contemporaries seem to have used star-based positions. India kept the star-fixed zodiac, and Western astrology has been mainly tropical since the Middle Ages.

The zodiac of twelve equal signs comes from Babylonian astronomy, and the Babylonians counted it from the stars (Wikipedia, "Zodiac"). Greek astronomers such as Geminus, in the first century BC, already tied the signs to the solstices and equinoxes. In the second century AD Ptolemy gave the reason for doing so in the Tetrabiblos:

it is reasonable to reckon the beginnings of the signs also from the equinoxes and solstices … their natures, powers, and familiarities take their cause from the solstitial and equinoctial starting-placesClaudius Ptolemy, Tetrabiblos I.22, tr. F. E. Robbins (LacusCurtius)

In other words, the signs get their qualities from the seasons: Aries from the start of spring, Cancer from the summer solstice. Not every astrologer of his time worked that way. In his notes for The Astrology Podcast, Chris Brennan writes that the Hellenistic astrologers "seem to have drawn on both tropical and sidereal considerations" ("The Zodiac Debate"). Kenneth Bowser, citing Neugebauer and Van Hoesen's Greek Horoscopes (1959), argues that many surviving Greek horoscopes, including those in Vettius Valens, were counted from star-based starting points rather than the equinox. His essay was written for the sidereal side of a debate (Skyscript).

India received much of its horoscopic astrology from Greek sources, above all the Yavanajataka, the "nativity according to the Greeks." Its translation from Greek into Sanskrit is traditionally dated to the second century AD, a date now disputed, and the text survives in a later verse version by Sphujidhvaja (Wikipedia, "Yavanajataka"). Indian astrology kept the star-fixed zodiac and adjusts for precession with the ayanamsa. Western astrology, following Ptolemy, has been mainly tropical since the Middle Ages.

Which zodiac do you use, and why?

I use the tropical zodiac, as Ptolemy did and as Western astrology mainly has since the Middle Ages. In Ptolemy, the qualities of the signs, hot and cold, moist and dry, come from the seasons, and the seasons come from the equinoxes. That is a choice of tradition, not a verdict that the other one is wrong.

Jyotish is a complete system of its own, with techniques built for the sidereal zodiac, such as the 27 nakshatras, the lunar mansions it uses alongside the signs. Medieval Arabic and European astrology used 28: the lunar mansions. A Vedic astrologer reads a sidereal chart with Vedic methods, and I read a tropical chart with the Hellenistic methods described in what Hellenistic astrology is. The confusion starts when the two get mixed: a Vedic reading of a tropical chart, or a Western reading of a sidereal one.

So if you have had a Vedic reading and a Western one and the signs disagree, nothing is broken. Each reading used its own map correctly. Keep each set of placements with the method that produced it.

Is Vedic astrology more accurate than Western astrology?

Neither has been shown to be more accurate. No branch of astrology has passed a controlled scientific test, and that includes the one I practice. Vedic and Western astrology are different traditions asking different questions of a chart, so the better one for you is the one whose method you want to learn, or be read by.

What often feels more accurate is depth. A full reading of a whole chart, in either zodiac, will say far more than a Sun sign horoscope in either zodiac, because it reads the Moon, the rising sign, the houses and the timing. When people compare a detailed Vedic reading with a one-line Western horoscope, they are comparing two different depths, not two zodiacs.

Is Ophiuchus the 13th zodiac sign?

No, not in either system. Ophiuchus is a constellation the Sun passes through from about November 30 to December 17, within the boundaries astronomers use today. Signs are twelve equal slices of the Sun's path, named after constellations but not the same thing, so neither the tropical nor the sidereal zodiac has a thirteenth sign.

The constellations along the Sun's path are star pictures of very different sizes. By the modern boundaries the Sun spends about 45 days in Virgo and only about 7 in Scorpius, and it crosses a corner of Ophiuchus, the Serpent Bearer, in between (Wikipedia, "Zodiac"). The signs were made equal on purpose, so that each is exactly a twelfth of the circle.

The names of the signs do come from those star pictures, and so do their myths, which I collect in the zodiac signs in Greek mythology. But in a chart, a sign is a measured stretch of 30 degrees, in both zodiacs.

When do the sidereal Sun signs start?

In 2026 the sidereal Sun signs start 24 to 26 days after the tropical ones: Aries on April 13 instead of March 20, and Capricorn on January 14, the day India celebrates as Makar Sankranti, the Sun's entry into sidereal Capricorn. The dates move about one day later every 72 years.

Dates are for 2026 in Pacific time, and they shift by a day from year to year. Makar Sankranti usually falls on January 14, or January 15 in some years. If you were born within a day of a change, use the finder above with your birth time.

Common questions about sidereal and tropical astrology

Do I have two birth charts? You have one sky with two sets of labels. Every planet is at the same point in both; the sign names on the points differ by about 24 degrees.

Does my rising sign change in a Vedic chart? Usually. The rising degree moves back by the same amount as everything else, so it falls in the sign before unless it sat in the last six degrees or so of its tropical sign.

Do my houses change? With whole-sign houses, the houses follow the rising sign, and since every planet moves back by the same amount, most planets keep their house. A planet changes house only when it crosses a sign edge and the rising degree doesn't, or the other way round.

Which one is my real sign? The one in the system you are using. In Western astrology, and in the readings on this site, it is your tropical sign. In a Vedic reading it is your sidereal sign.

Why does my Vedic app show a slightly different degree from this page? Usually because of the birth time or time zone it was given, daylight saving time included, or because it uses another ayanamsa, such as Raman's or Krishnamurti's. Lahiri is the most common. Whether an app quotes the ayanamsa with or without nutation, a small nod of the Earth's axis, changes that figure by at most 17 seconds of arc and does not move the sidereal position.

Does the weekday or Moon phase I was born on change? No. The weekday and the phase of the Moon are the same in both systems. You can find them with what day was I born and Moon phase when you were born.