How accurate is this?
A precise answer for the calculations, and an honest one for everything built on top of them.
The short version
The astronomy is accurate to a small fraction of a degree and can be checked against any professional ephemeris. The astrology is a traditional practice rooted in belief, and no amount of computational precision changes that. Those are different claims and we try never to blur them.
How the chart is calculated
- Planetary positions come from VSOP87 for the planets and ELP for the Moon — the same theories professional ephemerides are built on — including light-time and aberration corrections.
- The sidereal shift uses the Lahiri (Chitrapaksha) ayanamsa, adopted by the Indian government's calendar reform committee and the standard for Vedic work.
- Your birth moment is resolved through the IANA timezone that actually applied at that instant, not a fixed offset. India ran +5:53:20 until 1906 and only settled on +5:30 in 1955.
- The ascendant is computed from apparent sidereal time at your birth coordinates, which is why a real city and a real birth time are both required.
- Houses are whole-sign, the Parashari default and what almost every Indian chart uses.
What was actually tested
Not assertions — these are the checks the engine has to pass.
Meeus, Astronomical Algorithms, example 33.a
Venus apparent position, 1992 December 20.0 TD
RA 21h04m41.454s, Dec −18°53′16.84″ — exact match to the published value
March equinox, 2026
The Sun must sit at 0° tropical longitude
0.000°
Ascendant at sunrise, Delhi
By definition the Sun sits on the ascendant at sunrise
−1.21° at 05:23 IST, +0.40° at 05:30 — sunrise falls between them
Ascendant over one sidereal day
It must return to the same degree after 23h56m04s
0.02° drift
Moon against an independent implementation
Cross-checked against a separately written ELP routine
Both place the test chart's Moon at 18°55′ Taurus, Rohini
Vimshottari arithmetic
Sub-periods must exactly fill their parent period
Antardashas sum to the mahadasha; the cycle totals 120 years
Where it can still be wrong
- Your birth time. The ascendant moves a degree every four minutes. A time recorded to the nearest half-hour, which is common, can put the ascendant in the wrong sign entirely. This is by far the largest source of error and it is not something the software can fix.
- Pre-1906 births in India. Records from that period often used local mean time rather than any standard zone, which can shift the ascendant by several degrees. We apply the timezone database, which may not match how the time was originally noted.
- Ayanamsa choice. We use Lahiri. Raman and Krishnamurti differ by up to a degree, which occasionally moves a planet near a sign boundary.
- The nodes. We use the mean lunar node, standard in Vedic practice. The true node oscillates around it by up to 1.6°.
What we do not claim
- That astrology predicts anything. There is no scientific evidence for it, and we present the tradition as a tradition.
- That a reading here substitutes for medical, legal, financial or psychological advice. It does not, and the AI is instructed to hand those questions back.
- That we are connected to OpenAI. KundaliGPT is independent and not affiliated with, endorsed by, or built on ChatGPT.
If you find a calculation you believe is wrong, please tell us — send the birth details, the figure you got and the source you are comparing against.
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