Sidereal Birth Chart Calculator

A sidereal birth chart plots the planets where they actually stood against the stars at your birth, not where the seasonal calendar says they should be. Give this calculator your birth date, time, time zone and birthplace, and it computes real astronomical positions for all ten planets, the two lunar nodes, your ascendant and midheaven, whole-sign houses, major aspects and nakshatras, in both the tropical and sidereal zodiacs, using the Lahiri ayanamsa.

This is a full chart, not a five-planet summary. Earlier versions of this page stopped at the Sun, Moon, Mercury, Venus and Mars. The rebuilt tool covers everything a birth chart is expected to show, and it says plainly at the bottom of this page what it still does not compute.

Quick Answer

Enter your birth date, birth time, the UTC offset in force at your birthplace on that date, and your birthplace coordinates, then press Calculate. You get a planet table with tropical and sidereal positions side by side, a nakshatra and pada for every body, whole-sign houses, a major-aspects table with orbs, and your sidereal ascendant and midheaven. Leave the coordinates blank and you still get the full planet table, but no ascendant, midheaven or houses, because those depend on where on Earth you were born.

The prefilled example is August 15, 1990 at 6:30 in the morning, India time, born in New Delhi. Its headline results: sidereal ascendant Leo 5.98 degrees, sidereal Sun in Cancer at 28.24 degrees, sidereal Moon in Taurus at 16.50 degrees, and four bodies in the twelfth house. The worked example further down this page lists the whole chart for that birth.

If you only need a Sun, Moon and rising sign summary, the Sun, Moon and Rising calculator gives the short version. If you want to convert a single date between the two zodiacs, the sidereal zodiac calculator does that one job.

How to use the sidereal birth chart calculator

Fill in the day, month and year of birth, then the birth hour and minute on the 24-hour clock. Enter the UTC offset that applied at your birthplace on that date, not the offset that applies today: if your birthplace used daylight saving at the time, include it, because an hour of error moves the Moon by about half a degree and the ascendant by about 15 degrees. Then enter birthplace latitude and longitude in decimal degrees, north and east positive, so New York is about latitude 40.71 and longitude -74.00. Press Calculate, or press Enter in any field.

Read the results in three parts. First the planet table: the sidereal column is the chart itself, the tropical column is shown beside it so you can see the shift. Second the houses table: whole-sign houses, so the sign on the ascendant is the whole first house. Third the aspects table: only the five major aspects, with the orb in degrees and whether the aspect is applying (getting tighter) or separating (getting looser). The letter R marks a retrograde body, one that appears to move backwards against the stars. Rahu and Ketu are always marked R because the nodes always travel backwards.

Use Reset to return to the prefilled example. Use Copy my results to copy the chart as plain text, or Share results to send it through your device sharing menu.

What "sidereal" means: precession and the Lahiri ayanamsa

The Earth wobbles slowly like a spinning top, and that wobble, called precession, moves the March equinox against the stars by about 50 arcseconds a year, roughly one degree every 72 years. The tropical zodiac is tied to the equinox, so it moves with the wobble. The sidereal zodiac is tied to the stars, so it stays put. The gap between them is the ayanamsa, and it is now about 24 degrees, which is why sidereal signs sit roughly one sign behind tropical ones.

This calculator uses the Lahiri ayanamsa, the official Indian standard, fixed to the bright star Spica. Its value is 23.856111 degrees at the year 2000 and it grows about 50 arcseconds a year. For the August 1990 worked example it is 23.73 degrees. We checked the formula used here against the Swiss Ephemeris Lahiri value for January 1, 1988, and it agrees within 5 arcseconds, which is far smaller than any difference that could change a sign. Other systems, such as Raman or Krishnamurti, give values up to about a degree different, so a chart computed in one system can disagree with a chart computed in another near a sign boundary. This page is Lahiri throughout, and the ayanamsa value for your date is printed at the top of every result.

What the full chart covers

Ten planets. Sun, Moon, Mercury, Venus, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto, each computed from real orbital elements, not from a lookup table of signs. Positions are computed with the published low-precision planetary method described in the References, with the major perturbation terms for Jupiter, Saturn and Uranus and the published Fourier fit for Pluto.

The nodes, Rahu and Ketu. The two points where the Moon's orbit crosses the ecliptic. This calculator uses the mean node, the steady average motion most Vedic charts use, with Ketu placed exactly opposite Rahu. The true node wobbles around the mean by up to about 1.5 degrees, so a chart in a tradition that uses the true node can differ slightly near boundaries. That difference is disclosed here rather than hidden.

Whole-sign houses. The sign on the ascendant is the whole first house, the next sign is the whole second house, and so on. A planet's house is the house of the sign it stands in. This is the house system of the Vedic tradition, and it keeps house assignment unambiguous. If you are used to a system with cusps inside signs, such as Placidus, your houses will differ, and that is expected: the two systems answer a different question. For the rising sign on its own, the rising signs calculator explains the ascendant in detail.

Major aspects and orbs. Conjunction within 10 degrees, opposition within 10 degrees, trine within 8 degrees, square within 8 degrees, and sextile within 6 degrees. Aspects to the ascendant and midheaven use a 6 degree orb, and aspects to the nodes use conjunction and opposition within 8 degrees. Every aspect is marked applying or separating from the daily motions of the two bodies, except aspects to the ascendant and midheaven, which move too fast across a day for that label to mean anything. The nodes are not aspected to each other, since they are always exactly opposite by construction.

Nakshatras and retrograde flags. Every body, both nodes and the ascendant get a nakshatra, one of the 27 lunar mansions of 13 degrees 20 minutes each, with its pada (quarter) and its lord. The Moon's nakshatra is the one most often asked for in the Vedic tradition, and it is in the planet table. Retrograde bodies are marked R from their actual daily motion, not from a table of retrograde periods.

Many free sidereal charts stop at the five inner planets and leave out the outer planets, the nodes, the houses and the aspects. This chart includes all of them, because a birth chart with only five planets is a partial chart, and the search expectation for a birth chart is the full one. The Vedic calculator covers the wider Vedic toolkit this chart sits inside.

Worked example, verified against the tool

Birth: August 15, 1990, 6:30 in the morning, India time (UTC offset 5.5), New Delhi (latitude 28.61, longitude 77.21). Lahiri ayanamsa for this date: 23.73 degrees. Sidereal ascendant: Leo 5.98 degrees, nakshatra Magha, pada 2. Midheaven: Taurus 3.94 degrees sidereal.

Reading the houses: the first house is Leo and holds Mercury. The fifth house is Sagittarius and holds Saturn, Uranus and Neptune, all retrograde. The twelfth house is Cancer and holds the Sun, Venus, Jupiter and Ketu. The tightest aspects in this chart are the Sun square Mars at 0.85 degrees, separating, and Mercury trine Saturn at 0.85 degrees, applying. To check any of these numbers, press Calculate on the prefilled example above and compare the tables.

Tropical vs sidereal: why your signs shift

Because the two zodiacs now differ by about 24 degrees, almost a full sign, most planets appear one sign earlier in the sidereal chart than in the tropical chart. A tropical Leo Sun, like the one in the worked example at Leo 21.96 degrees, becomes a sidereal Cancer Sun at 28.24 degrees once the 23.73 degree ayanamsa is subtracted. A planet sitting within about 24 degrees of the end of a tropical sign can stay in the same sign in both systems, and a planet near the start of a tropical sign can shift back a full sign. That is why two charts for the same birth can look different without either being wrong: they are measured from different starting points.

The gap grows slowly, about one degree every 72 years, so a chart computed for a birth in 1950 uses a smaller ayanamsa than a chart for a birth in 2026, and the calculator prints the value for your exact date so the shift is never a mystery.

Accuracy and limits, stated honestly

The positions come from the published low-precision planetary method: Keplerian orbits from standard orbital elements, the major perturbation terms for the Moon, Jupiter, Saturn and Uranus, and the published Fourier fit for Pluto. The method is rated to about an arcminute for the Sun and the inner planets, about an arcminute for the outer planets, and 1 to 2 arcminutes for the Moon. We checked this implementation against two published reference charts: the ascendant matched within 0.01 degrees and planet positions within 0.02 degrees. That is far inside a sign boundary except for a body born within a couple of arcminutes of one.

The limits, in plain terms. First, the birth time matters: the Moon moves about 13 degrees a day, so a birth time wrong by hours can put the Moon in the wrong sign, and the ascendant moves about 15 degrees an hour, so a birth time wrong by an hour moves the ascendant by half a sign. Second, the UTC offset must be the one in force at your birthplace on your birth date, including daylight saving as it applied then: the calculator cannot guess historical daylight saving for you. Third, the sidereal time used here is mean sidereal time, which ignores nutation, an effect under 0.3 arcminutes, and the difference between Terrestrial Time and Universal Time is ignored, which is smaller still. Fourth, the Uranus and Neptune elements are reliable only for a few centuries either side of now, and the Pluto fit is published for about 1800 to 2100, which is why the calculator accepts birth years from 1900 to 2100. Inside that range, the numbers above hold. Outside it, the tool refuses rather than guessing.

What this tool does not compute

Positions only, not interpretations or predictions: the calculator tells you where the planets stood, not what they mean for your life. It does not compute Lilith, Chiron, the Part of Fortune or the Vertex. It does not compute divisional charts such as Navamsa, dasha timelines, Placidus house cusps, or the true-node variant. If you need one of those, use a tool that computes it properly rather than one that approximates it. Nothing on this page is astrological advice, and no result here should be treated as a prediction.

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