What Determines Chart Accuracy

This question usually gets answered as a tradition pick, Vedic or Western, when the bigger factors determining a chart's accuracy sit somewhere else entirely: how precise the birth data is, and how rigorously the calculation is actually done.

Birth Time Precision Beats Tradition Choice

A chart calculated from a birth time that's off by even fifteen minutes can shift the Rising sign and every house cusp that follows from it, regardless of which zodiac or tradition is used. This single factor moves the needle on accuracy more than the tropical-versus-sidereal choice ever does, since it affects the geometry of the whole chart, not just where the signs get labeled.

Calculation method matters almost as much. A tool using real orbital mechanics, actual ephemeris data for planetary positions, will differ from one using a simplified lookup table, especially for anything involving exact degrees rather than just which sign a planet occupies. The gap is usually small for Sun and Moon sign placement, and can be meaningfully larger for house cusps, aspects, and divisional charts, where precision compounds.

Within Vedic astrology specifically, ayanamsa choice adds one more variable. Lahiri, Raman, and other ayanamsas can shift a placement near a sign boundary from one sign into the next, which is a real source of disagreement between two otherwise correctly calculated sidereal charts.

So the honest answer to "which chart type is most accurate" isn't a tradition, it's a standard: exact birth data, transparent calculation method, and a disclosed ayanamsa if the chart is sidereal. A chart meeting that standard is more trustworthy than one that doesn't, independent of which zodiac it's built on.