Technical Methodology
How VedicBirth Calculates Your Kundli
Every number on the site comes from Swiss Ephemeris and the Lahiri ayanamsha. This page documents the full calculation pipeline.
Astronomical source
Planetary longitudes, latitudes, and speeds come from Swiss Ephemeris, a high-precision library derived from the NASA JPL DE431 ephemeris and widely used in professional astronomical software. Given a birth date, time, and place, we compute tropical longitudes for the Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn, and the mean Rahu and Ketu nodes, and then convert each to a sidereal longitude by subtracting the ayanamsha value for that moment.
Ayanamsha: Lahiri
VedicBirth uses Lahiri Chitrapaksha as the default ayanamsha. It is the standard adopted by the Indian government through the Rashtriya Panchang and is the most widely accepted ayanamsha among practising Jyotish pandits in India. Other sidereal conventions such as Raman or Krishnamurti will produce different rashi boundaries, so if you compare a VedicBirth chart against a tool using a different ayanamsha, planets near a sign cusp may appear to move.
Houses and aspects
Houses use the whole-sign system, where the rashi rising on the eastern horizon becomes the first bhava in full, the next rashi is the second bhava, and so on. This is the oldest method documented in classical Parashari literature. Graha drishti, the aspect system used in interpretations, follows Brihat Parashara Hora Shastra: every planet aspects the seventh house from its own, Mars adds the fourth and eighth, Jupiter adds the fifth and ninth, and Saturn adds the third and tenth.
Nakshatras and divisional charts
The 360 degree sidereal zodiac divides into twenty-seven nakshatras of 13 degrees 20 minutes each, and each nakshatra further divides into four padas of 3 degrees 20 minutes. We compute the nakshatra and pada for every planet and for the ascendant, and we apply the nakshatra lord both for planetary interpretation and for Vimshottari dasha calculation. On request the site produces sixteen divisional charts (vargas), including Navamsa, Dashamsa, Saptamsa, Shodasamsa, and Trimsamsa, built from the sidereal longitude according to the standard Parashari division rules.
Vimshottari dasha
Dasha periods follow the one hundred and twenty year Vimshottari cycle. The cycle begins from the nakshatra held by the Moon at birth, with the balance of the first mahadasha prorated by how far the Moon has travelled through that nakshatra. The planet ordering (Ketu, Venus, Sun, Moon, Mars, Rahu, Jupiter, Saturn, Mercury) and the fixed lengths in years (7, 20, 6, 10, 7, 18, 16, 19, 17) come straight from Parashara. Antardasha and pratyantar dasha are computed by multiplying the parent period by the ratio of the sub-lord years to 120 and 120-squared respectively.
Verification
Every release of VedicBirth is cross-checked against printed regional panchangs, notably the Kalnirnay and the Rashtriya Panchang, for a sample of dates spanning the twentieth and twenty-first centuries. Tithi, nakshatra, yoga, and karana at sunrise are compared entry by entry, and discrepancies are traced to either an ayanamsha mismatch or a rounding difference and documented in the changelog.
Corrections
Spotted a calculation that disagrees with a classical source or a trusted panchang? Write to hello@vedicbirth.com with the birth data, the value you computed, and the source you used. The author is Aniket Nigam.