Nakshatra Calculator

What is a nakshatra?

The Moon circles the sky in about 27.3 days. The Indian tradition divides its path into nakshatras, often called lunar mansions, and the Moon spends roughly one day in each. We use the later and most common division: 27 equal parts of 13°20′, each split into four padas of 3°20′, which makes 108 padas in all.

Older lists have 28 nakshatras, including Abhijit, with parts of unequal width. Abhijit is mentioned in the tradition, for instance for choosing favourable times, but it is not part of the 27 that this calculator uses.

Sidereal, not tropical

Western astrology measures the zodiac from the March equinox (the tropical zodiac). Vedic astrology fixes the zero point against the stars (the sidereal zodiac). The difference is called the ayanamsa. It grows by about 50 arcseconds a year because of the precession of the equinoxes. With the Lahiri ayanamsa it was 24°13′ on 1 January 2026.

As a result the Sun is, for roughly the first 24 days of each tropical sign, still in the previous sidereal sign, and for the last 6 days or so in the same one. The twelve rashi are equal parts of 30° from the chosen zero point, not the constellations with their official boundaries.

How we calculate

We take the Moon's apparent position as seen from the centre of the Earth from the Astronomy Engine library, correct it for nutation, and subtract the ayanamsa. The nakshatra is the 13°20′ part that contains the result; the begin and end times are found by searching for the moments the Moon crosses the boundaries. Everything runs in your browser, for dates from 1900 to 2100.

We checked the Moon's position against the moon phases of the U.S. Naval Observatory and the ayanamsa against a published table from the Swiss Ephemeris. We also compared 38 nakshatra boundary times on 19 dates between 1901 and 2030 with the daily Panchang of Prokerala (Lahiri ayanamsa, local time in India). That is a calculation, not an official almanac. The largest difference was 1.1 minutes. Before 1906 India had no single standard time, and the published times follow the historical time zone data (UTC+5:21 until the end of 1905). For dates after 2030 we have no published source to compare with, and we have not yet compared the results with the Indian Astronomical Ephemeris or the Rashtriya Panchang.

Our choices

• Ayanamsa: Lahiri (Chitrapaksha), the official standard in India. You can switch to Raman, Krishnamurti, Fagan-Bradley or True Chitrapaksha; the value used is always shown.
• Division: 27 equal nakshatras. Abhijit is explained but not calculated.
• Position: geocentric, that is as seen from the centre of the Earth, not from your birthplace. The difference for the Moon is up to about 1°, which can matter near a boundary.
• Time: your birth time in the time zone you choose, with India Standard Time (UTC+5:30) shown next to it for every date. India adopted that standard in 1906; for earlier births choose Asia/Kolkata to get the local time of the day.

What this calculator does not do

It gives positions, not predictions. What a nakshatra means for a person is part of the tradition, and where we mention it we say so. We do not offer compatibility matching.

Sources and further reading

• Kim Plofker, Mathematics in India (Princeton University Press, 2009).
• David Pingree, Jyotiḥśāstra: Astral and Mathematical Literature (Otto Harrassowitz, 1981).
• Ebenezer Burgess, Translation of the Sûrya-Siddhânta, Journal of the American Oriental Society 6 (1860), pp. 141–498 (public domain).
• William Sewell and Sankara Balkrishna Dikshit, The Indian Calendar (1896; public domain).
• Swiss Ephemeris documentation, table of ayanamsa systems (values for Lahiri, Raman, Krishnamurti and Fagan-Bradley).
• Astronomy Engine (positions of the Sun, Moon and planets) and the moon phases of the U.S. Naval Observatory (test of the Moon's position).
• Prokerala, daily Panchang (Lahiri ayanamsa, India Standard Time), used to compare nakshatra boundary times.