Sidereal Sun, Moon, ascendant and dasha, honestly scoped
A Vedic chart is placed on the sidereal zodiac, the star-fixed frame, using an ayanamsa to convert from the tropical positions astronomy publishes. This calculator computes, with documented astronomy, the placements that can be computed and checked to the standard this site requires: the Sun and Moon sidereal signs and degrees, the Moon’s nakshatra and pada, the mean lunar nodes (Rahu and Ketu), the ascendant (Lagna) when birth time and place are given, whole-sign houses from the Lagna, and the Vimshottari dasha sequence that follows from the Moon’s nakshatra. It deliberately does not print positions for Mars, Mercury, Jupiter, Venus or Saturn: those need a full precision ephemeris, and this page will not dress approximations up as a complete chart. What it does compute, it computes properly, and the method section says exactly how.
Disclaimer: This calculator gives estimates for general information only. It is not financial, medical or other professional advice. Vedic astrology is a traditional interpretive system presented here for cultural interest and entertainment; its readings are not scientific findings, and this page computes placements and periods without offering predictions or life guidance.
What this calculator does
It builds the verified core of a janma kundli. Tropical longitudes for the Sun and Moon are computed from standard orbital elements (the Sun to within about a hundredth of a degree, the Moon to within a few arc-minutes using the principal perturbation terms), converted to sidereal with the Lahiri ayanamsa, and expressed as sign and degree. The Moon’s sidereal longitude gives the nakshatra (the 27 lunar mansions of 13 degrees 20 minutes each) and its pada (quarter), and from the nakshatra’s lord and the fraction of it traversed, the Vimshottari dasha balance and the full 120-year mahadasha sequence with calendar dates. Given a birth time and coordinates, sidereal time yields the Lagna, and houses are the whole signs counted from it, the standard Vedic method. Rahu and Ketu are placed at the Moon’s mean ascending node and its opposite point, labelled as mean positions, as most traditional software defaults.
How to use it
- Birth time quality sets the Lagna’s worth. The ascendant crosses a sign roughly every two hours and moves about a degree every four minutes, so a time rounded to the hour can put the Lagna near a sign edge. The results flag a Lagna within 2 degrees of a sign boundary as time-sensitive; treat such a chart’s house placements as provisional, a caveat practitioners themselves apply.
- The UTC offset is the historical one. Time zones and daylight rules have changed repeatedly (wartime doubles, redefined zones). Use the offset actually in force at the birthplace on the birth date; a one-hour error has the same effect as a one-hour birth-time error.
- The Moon sign and nakshatra are the traditional headline. Where Western charts lead with the Sun sign, Vedic practice leads with the Moon’s sign (chandra rashi) and nakshatra, which also seed the dasha. Those are the figures to take from this page first.
- Dates in the dasha list are period boundaries, not predictions. The Vimshottari system assigns life periods to planetary lords in a fixed order scaled by the Moon’s progress through its birth nakshatra. The page computes the timetable exactly as the tradition defines it and offers no interpretation of what any period will bring.
- For the remaining planets, use an ephemeris-based tool. This page states its scope rather than silently approximating Mars through Saturn. A full professional chart also adds divisional charts (navamsha and beyond); only independently verifiable outputs are implemented here, per this site’s method.
How it is calculated
- Positions: the Sun’s and Moon’s tropical ecliptic longitudes are computed from published mean orbital elements with the equation of centre for the Sun and the Moon’s principal perturbations (evection, variation and the yearly equation among them). The implementation was validated against the solar eclipse of 8 April 2024 (computed Sun and Moon within a few hundredths of a degree of each other at conjunction) and the full moon of 24 February 2024 (opposition within 0.02 degrees).
- Ayanamsa (Lahiri): 23.85306 degrees at 1 January 2000, increasing 0.0139697 degrees per year (50.29 arc-seconds), the standard linear form of the Lahiri value used by the Indian calendar reform tradition. Sidereal longitude = tropical longitude – ayanamsa for the date.
- Lagna: from Greenwich mean sidereal time (280.46061837 degrees at J2000 plus 360.98564736629 degrees per day), local sidereal time by longitude, and the standard ascendant formula with obliquity 23.4393 degrees, minus the ayanamsa. Houses are whole signs from the Lagna sign.
- Vimshottari dasha: the birth nakshatra’s lord owns the first period; its remaining length is the untraversed fraction of the nakshatra times the lord’s full years (Ketu 7, Venus 20, Sun 6, Moon 10, Mars 7, Rahu 18, Jupiter 16, Saturn 19, Mercury 17, totalling 120), and subsequent periods follow in that fixed order, dated with 365.25-day years.
Worked examples
17 May 1990, 10:30 in London (latitude 51.5, longitude -0.13, offset +1). Ayanamsa for the date: 23.72 degrees. Sun sidereal 32.51 degrees, Taurus 2.51. Moon sidereal 297.55 degrees, Capricorn 27.55, in Dhanishta, pada 2. Mean Rahu at Capricorn 17.52, Ketu opposite in Cancer. Lagna sidereal 105.20 degrees, Cancer 15.20, so the Moon sits in the seventh whole-sign house and the Sun in the eleventh, counted from Cancer. Dasha: Dhanishta’s lord is Mars; with 31.63% of the nakshatra traversed, the Mars balance is 4.79 years, running to 1 March 1995, then Rahu to 28 February 2013, then Jupiter to 28 February 2029.
Reading the scope from the same example. Everything printed above is either orbital arithmetic or calendar arithmetic, reproducible from the stated formulas. Conspicuously absent, by design: Mars in that chart, Jupiter, the navamsha. A site willing to print those owes the visitor a real ephemeris behind them; until then this page’s contract is the smaller, verifiable set, stated on its face.
Reading your results
Read the Moon sign and nakshatra first (the tradition’s anchor), the Lagna second and with its boundary flag in mind, and the dasha list as a timetable the tradition keeps, not a forecast this page makes. Compare like with like when checking against other tools: a tropical chart will differ from this sidereal one by roughly the ayanamsa (about 24 degrees, most of a sign), and a tool using a different ayanamsa (Raman, Krishnamurti) will differ by its small offset from Lahiri; both differences are conventions, not errors, and the method lines here state which conventions you are holding.
Limitations
- Five grahas are not computed. Mars, Mercury, Jupiter, Venus and Saturn are absent, not approximated. The chart core here (Lagna, Sun, Moon, nodes, nakshatra, dasha) is the part verifiable to this site’s standard with documented in-page astronomy; a complete traditional chart requires a licensed precision ephemeris.
- Ayanamsa is the linear Lahiri form. Exact Lahiri values from an ephemeris differ by small arc-second amounts from the linear formula; sign placements are unaffected except for bodies within a few arc-minutes of a sign or nakshatra edge, and the Moon’s pada near a quarter boundary is the figure to treat gently.
- Mean nodes, not true nodes. Rahu and Ketu are placed at the mean node, the traditional default in most software; the true node oscillates around it by up to about 1.5 degrees, which can matter at a sign edge.
- Local time is as entered. The page trusts the recorded birth time and the offset you supply; it does not adjudicate historical time-zone disputes or birth-record rounding, both of which are real and common, and both land on the Lagna first.
Frequently asked questions
What is the difference between Vedic and Western charts?
The zodiac frame: Western astrology uses the tropical zodiac, anchored to the equinoxes, while Vedic astrology uses the sidereal zodiac, anchored to the stars, and the two have drifted apart by the ayanamsa, about 23.72 degrees in 1990 and about 24 degrees today. The same birth moment therefore yields different signs in the two systems (a tropical Gemini Sun of late May is a sidereal Taurus Sun here), and both are internally consistent. Vedic practice also leads with the Moon sign and nakshatra and times its dasha periods from the Moon, which is why this calculator centres them.
What is an ayanamsa?
The accumulated angle between the tropical and sidereal zodiacs for a date, subtracted from tropical longitudes to get sidereal ones. Several named ayanamsas exist, differing by fractions of a degree; Lahiri is the most widely used in Indian practice and the one this page applies in its standard linear form, with the constants printed in the method section so the conversion can be audited or redone under another ayanamsa by hand.
What is a nakshatra?
One of 27 lunar mansions dividing the sidereal zodiac into spans of 13 degrees 20 minutes, each with a ruling planet in the dasha system and each quartered into padas of 3 degrees 20 minutes. The Moon’s nakshatra at birth is among the most-used facts in Vedic practice (it names the janma nakshatra and seeds the Vimshottari timetable). In the worked example the Moon at Capricorn 27.55 falls in Dhanishta, pada 2, and the dasha arithmetic follows directly from that placement.
What is the Vimshottari dasha?
The 120-year cycle of planetary periods (mahadashas) that times traditional Vedic interpretation: nine lords in fixed order with fixed year-lengths, the first period shortened to the balance implied by the Moon’s progress through its birth nakshatra. This page computes the sequence and its calendar boundaries from the birth moment, with 365.25-day years, and prints it as the tradition’s timetable. What any period signifies belongs to interpretive practice, which the page does not perform.
Related calculators
Method: sidereal placements from documented orbital elements with the Lahiri ayanamsa in linear form, mean nodes, GMST-based Lagna and whole-sign houses, and Vimshottari periods from the Moon’s nakshatra, exactly as defined on this page. Other grahas intentionally not computed. Last reviewed: 13 October 2026.