What is a birth nakshatra (janma nakshatra)?
Your birth nakshatra is the lunar mansion the Moon occupied at the precise moment you were born. The sidereal zodiac is divided into 27 equal nakshatras of 13°20' each, and the Moon's position in that chain at your birth is your astrological identity in Tamil tradition.
Birth nakshatra is not the same as your Sun sign in Western astrology. It is also not the same as your rashi (Moon sign). Nakshatra is a finer division, it distinguishes between people who share the same rashi and gives each person a precise starting point for tarabalam, chandrashtamam, porutham, and naming.
Why birth time matters, not just the date
The Moon moves about 13° per day along the zodiac. Each nakshatra spans 13°20', so the Moon crosses one entire nakshatra in roughly 24 hours. Two people born on the same day but hours apart can have different nakshatras, especially if the birth falls near a nakshatra boundary.
The 27 nakshatras and their rashis
Each rashi (zodiac sign) holds exactly 2.25 nakshatras, that is, 9 padas. The pattern is 2-2-3: two nakshatras with all 4 padas in the sign, followed by one nakshatra shared between two signs. The table below maps all 27 nakshatras to their rashis.
| No. | Nakshatra (Tamil) | Transliteration | Degrees | Rashi (padas) |
|---|---|---|---|---|
| 1 | அசுவினி | Ashwini | 0°–13°20' | Mesha (all 4) |
| 2 | பரணி | Bharani | 13°20'–26°40' | Mesha (all 4) |
| 3 | கார்த்திகை | Krittikai | 26°40'–40° | Mesha (1) / Rishabha (2–4) |
| 4 | ரோகிணி | Rohini | 40°–53°20' | Rishabha (all 4) |
| 5 | மிருகசீரிடம் | Mrigashirsham | 53°20'–66°40' | Rishabha (1–2) / Mithuna (3–4) |
| 6 | திருவாதிரை | Thiruvadhirai | 66°40'–80° | Mithuna (all 4) |
| 7 | புனர்பூசம் | Punarpoosam | 80°–93°20' | Mithuna (1–3) / Kataka (4) |
| 8 | பூசம் | Poosam | 93°20'–106°40' | Kataka (all 4) |
| 9 | ஆயில்யம் | Ayilyam | 106°40'–120° | Kataka (all 4) |
| 10 | மகம் | Magam | 120°–133°20' | Simma (all 4) |
| 11 | பூரம் | Pooram | 133°20'–146°40' | Simma (all 4) |
| 12 | உத்திரம் | Uthiram | 146°40'–160° | Simma (1–2) / Kanni (3–4) |
| 13 | அஸ்தம் | Astham | 160°–173°20' | Kanni (all 4) |
| 14 | சித்திரை | Chithirai | 173°20'–186°40' | Kanni (1–2) / Thula (3–4) |
| 15 | சுவாதி | Swathi | 186°40'–200° | Thula (all 4) |
| 16 | விசாகம் | Visakam | 200°–213°20' | Thula (1–3) / Vrischika (4) |
| 17 | அனுஷம் | Anusham | 213°20'–226°40' | Vrischika (all 4) |
| 18 | கேட்டை | Kettai | 226°40'–240° | Vrischika (all 4) |
| 19 | மூலம் | Moolam | 240°–253°20' | Dhanus (all 4) |
| 20 | பூராடம் | Pooradam | 253°20'–266°40' | Dhanus (all 4) |
| 21 | உத்திராடம் | Uthiradam | 266°40'–280° | Dhanus (1–2) / Makara (3–4) |
| 22 | திருவோணம் | Thiruvonam | 280°–293°20' | Makara (all 4) |
| 23 | அவிட்டம் | Avittam | 293°20'–306°40' | Makara (1–2) / Kumbha (3–4) |
| 24 | சதயம் | Sadhayam | 306°40'–320° | Kumbha (all 4) |
| 25 | பூரட்டாதி | Poorattadhi | 320°–333°20' | Kumbha (1–3) / Meena (4) |
| 26 | உத்திரட்டாதி | Uthirattadhi | 333°20'–346°40' | Meena (all 4) |
| 27 | ரேவதி | Revathi | 346°40'–360° | Meena (all 4) |
How to find your birth nakshatra, step by step
Finding your janma nakshatra requires four pieces of information and an astronomical calculation:
- Know your exact birth date, birth time, and birthplace.
- Calculate the Moon's tropical longitude for the exact birth moment (converted to Universal Time).
- Subtract the Lahiri ayanamsa to get the Moon's sidereal longitude.
- Divide the sidereal longitude by 13°20' (= 13.333°). The integer part is the nakshatra index (0 = Ashwini, 1 = Bharani, etc.).
- The remainder divided by 3°20' (= 3.333°) gives the pada (1–4).
Worked example
Example: birth on 15 March 2000, 2:30 PM, Chennai
- Moon's tropical longitude (Meeus ch. 47)
- 187.52°
- Lahiri ayanamsa (2000)
- 23.86°
- Moon's sidereal longitude
- 187.52° - 23.86° = 163.66°
- Nakshatra index
- floor(163.66 / 13.333) = 12 = Astham (no. 13)
- Pada
- floor((163.66 - 160) / 3.333) + 1 = 2 = Astham pada 2
- Rashi
- Astham pada 2 = Kanni (Virgo)
Birth nakshatra: Astham, pada 2, rashi Kanni.
Numbers in this example are rounded for clarity. A real calculator uses full precision.
The 4 padas, each nakshatra's four quarters
Each nakshatra is divided into four equal parts called padas (quarters), each spanning 3°20'. The pada is not just a subdivision, it has concrete significance:
- The pada determines your rashi when the nakshatra is shared between two signs. Krittikai pada 1 gives Mesha; padas 2–4 give Rishabha.
- The pada determines your naming syllable. Each quarter assigns a specific syllable used to choose the child's name at the namakaranam ceremony.
- The pada is used in porutham (marriage compatibility), where detailed calculations require the pada, not just the nakshatra.
Nakshatra vs. rashi vs. lagnam
Three concepts that are often confused but measure entirely different things:
| Concept | What it is | Division | What it depends on |
|---|---|---|---|
| Nakshatra | The Moon's exact position in the lunar mansions | 27 parts of 13°20' | Birth time (changes roughly every 24 hours) |
| Rashi | The Moon's zodiac sign, derived from nakshatra + pada | 12 signs of 30° | Birth time (changes roughly every 2.5 days) |
| Lagnam | The zodiac sign rising above the horizon | 12 signs of 30° | Birth time AND birthplace (changes roughly every 2 hours) |
Your nakshatra changes slowly (roughly once a day), your rashi even more slowly (roughly every 2.5 days), but your lagnam rotates through all 12 signs in 24 hours. Lagnam is therefore the most time-sensitive of the three.
Why accuracy requires an ephemeris
The Moon moves about 13° per day, but its speed varies between roughly 11.5° and 14.5° depending on the Moon's distance from Earth (its elliptical orbit). Near a nakshatra boundary, even one hour of uncertainty in the birth time can mean the difference between two nakshatras.
Our calculator uses Jean Meeus' 60-term series for the Moon's position (Astronomical Algorithms, chapter 47) and Lahiri (Chitrapaksha) ayanamsa based on 23.85° at J2000.0. This combination is the standard for Tamil panchangams and the Indian government's official calendar.
What to do if you don't know your exact birth time
Many people, especially from older generations, do not know their exact birth time. Here is what you can do:
- Ask family members, parents, grandparents, or others present at the birth often remember an approximate time.
- Check hospital records, many hospitals record the time in the birth register, even if it does not appear on the birth certificate.
- Look for an old jathakam, if the family had a horoscope prepared at birth, it typically contains the birth time the astrologer used.
- Consult an astrologer experienced in prashna, prashna (horary astrology) can be used to rectify the birth time based on the moment the question is asked.