Suba JathagamHow we calculate
A jathagam is calculated, not looked up
Every chart on Suba Jathagam is computed inside your phone or browser from the date, time and place of birth. Nothing is copied from another website, and your details are never sent to our server.
1. Where the planets were
We work out the exact positions of the Sun, Moon and planets at the birth moment with astronomy-engine, an open-source astronomical library built on the same planetary models astronomers use (VSOP87 and modern lunar theory). Positions are corrected for nutation and converted to the sidereal zodiac with the Lahiri ayanamsa, the standard adopted by the Government of India.
2. Turning the sky into a jathagam
Our own code then finds the Lagna from local sidereal time and latitude; rasi and whole-sign houses; nakshatra and pada (13°20′ and 3°20′ each); navamsa; tithi (each 12° of Moon–Sun angle), yoga and karana; Vimshottari dasa and bhukti from the Moon’s progress through its star; Mars, Rahu–Ketu and Kala Sarpa doshas; and the day’s panchangam from the real sunrise and sunset at the birth place.
3. Calendars and matching
Tamil months follow the sankranti-before-sunset rule, Kerala months the 3/5-of-daylight rule, and Telugu, Kannada and Hindi months the amanta and purnimanta lunar calendars with adhika masa. Matching uses the 10 porutham (counted from the bride’s star) and the 36-guna Ashtakoota with Nadi and Bhakoot dosha exceptions; where traditions differ, the page says so.
4. How accurate is it?
We compared 400 random charts between 1900 and 2060 with Swiss Ephemeris, the professional reference. Planets matched within a few arc-seconds (median 1–3″), the Lagna within half an arc-second on average, and there were no differences in sign, nakshatra or Lagna.
What astronomy can’t settle
Calculation is exact; interpretation is tradition. Different schools use different ayanamsas, Rahu node types and porutham rules — you can switch the node type and tradition in Settings. Please treat astrology as guidance, not certainty.