Ayanamsa = precession correction, the difference between tropical (Western) and sidereal (Vedic) zodiac positions. Parashara-based systems typically use Lahiri ayanamsa (also called "Indian standard ayanamsa").
KP uses its own ayanamsa, slightly different from Lahiri. In 2024:
Lahiri ayanamsa ≈ 23°56'
KP ayanamsa ≈ 23°12'
Difference ≈ 44 minutes, which moves planets by less than 1 sign but can shift nakshatra boundaries. This matters for horary (prashna) charts, where precision is critical.
Historical reason: K. Krishnamurti calibrated his ayanamsa to match his own observation data and horary results, rather than adopting Lahiri wholesale. Some schools claim KP ayanamsa is more accurate for horary; others argue they are equivalent for natal charts but diverge in horary.
Practical implication: A client's horoscope computed in KP using KP ayanamsa will show planets in slightly different positions than if computed in Parashara using Lahiri. For most purposes, the difference is negligible; for horary (Prashna) and event timing, it can matter.
The calculator uses KP ayanamsa for all KP computations. When comparing KP results to Parashara (Lahiri ayanamsa) results, note that the ayanamsa difference is one source of divergence.
You will compute the same chart in both ayanamsas and observe the difference. For most placements, it is under 1°; for some nakshatras, it can cross a boundary.
Why a few arc-minutes matter here. In rasi-level work an ayanamsa difference of six arc-minutes is invisible: a planet at 14 degrees of Taurus stays in Taurus. In KP the same difference can move a planet across a sub boundary, which changes the sub-lord, which changes the answer. The precision of the method is exactly what makes the ayanamsa choice non-negotiable.
The practical rule. Use KP ayanamsa with KP sub-lord tables and KP technique. Use Lahiri with classical Parashari work. Do not mix them. A chart cast with Lahiri and read against a KP sub-lord table will be correct most of the time and catastrophically wrong near boundaries, which is the worst possible failure pattern because it is hard to detect.
Checking your software. Most astrology software lets you set the ayanamsa explicitly. Before trusting any KP output, confirm which ayanamsa the program used, and confirm it did not silently fall back to a default. When two programs disagree on a sub-lord, the ayanamsa setting is the first thing to check.
What this does not mean. The existence of competing ayanamsas is sometimes presented as proof that sidereal astrology is arbitrary. That overstates the case: the disagreement is a few arc-minutes over a shared framework, not a dispute about where the stars are. But it does mean a practitioner must state which standard they used.