Understanding the calculations

What is ayanamsha, and which one should you use?

Ayanamsha is the angular gap between the tropical zodiac (measured from the spring equinox) and the sidereal zodiac (measured from a fixed star reference). Vedic astrology works in the sidereal zodiac, so every chart is cast by subtracting the ayanamsha from a modern tropical longitude — and because the equinox drifts by about 50 arc-seconds a year, the ayanamsha grows by that much every year.

Sarathi Services TeamUpdated 8 September 2026

Written and reviewed by the team that builds the Jyotish Sarathi calculation engine.

Key takeaways

Ayanamsha = tropical longitude − sidereal longitude. Subtract it to get the nirayana position jyotish uses.
It grows by roughly 50 arc-seconds per year (about 1° every 72 years) because of precession.
Systems disagree about where the fixed zodiac starts. Lahiri is the most widely used and India's official standard.
Raman sits roughly a degree and a half behind Lahiri — enough to move a nakshatra pada. Krishnamurti is only a few arc-minutes from Lahiri, but KP's fine sub-divisions still feel it.
The ayanamsha choice usually moves a chart more than the choice between Surya and Drik Siddhanta. Pick one deliberately and stay consistent.

Two zodiacs, one sky

Modern astronomy measures celestial longitude from the vernal equinox — the point where the Sun crosses the celestial equator in March. That is the tropical (sayana) zodiac, and it is tied to the seasons.

Vedic astrology measures from a fixed point among the stars. That is the sidereal (nirayana) zodiac, and it is tied to the constellations. When the two systems were aligned, roughly in the early centuries of the common era, there was no gap. There is one now.

Why the gap keeps growing

The Earth's axis wobbles, completing one circuit in roughly 25,800 years. The equinox therefore slides backwards along the ecliptic at about 50.3 arc-seconds a year — the precession of the equinoxes. The stars stay put; the reference point moves.

So the ayanamsha is not a constant you look up once. It is a function of the date. About 1° accumulates every 72 years, which is why a chart cast for 1950 and one cast for 2026 use noticeably different values, and why software has to compute it rather than store it.

The systems, and why they disagree

Every ayanamsha system is an answer to one question: where exactly does the sidereal zodiac begin? The classical texts do not fix it to modern precision, so different authorities anchored it differently — some to the star Spica (Chitra), some to Revati, some by working backwards from a historical date of alignment.

System	Anchor / basis	Relative to Lahiri
Lahiri (Chitrapaksha)	Places Spica (Chitra) at 180° of the sidereal zodiac	— (the reference)
Raman	B. V. Raman's value, derived from a different epoch of alignment	Roughly 1.5° behind
Krishnamurti (KP)	K. S. Krishnamurti's value, used in KP practice	A few arc-minutes behind
Others in the app	Additional systems including Fagan-Bradley-style Western sidereal values	Varies

Lahiri is the official ayanamsha of the Indian national calendar and the default in most Indian and Nepali practice. That is a reason to prefer it, but not a reason to override a lineage that uses something else.

What actually changes in a chart

A degree and a half sounds small until you see what it lands on:

Nakshatra pada — a pada is 3°20′ wide. A 1.5° shift moves a planet across a pada boundary in about half of all cases.
Nakshatra itself — 13°20′ wide, so a planet within 1.5° of a boundary changes nakshatra entirely.
Vimshottari dasha balance at birth — computed from the Moon's exact position in its nakshatra, so it changes whenever that position changes.
Rashi — only for planets sitting within about 1.5° of a sign boundary, but those cases are exactly the contentious ones.
KP sub-lords — the narrowest KP sub-division is well under a degree, so even the small Lahiri-to-Krishnamurti difference can flip a sub-lord.

How to choose, practically

1If you were taught one, use that one. Consistency with your parampara and your own past readings is worth more than any theoretical argument about the true anchor point.
2If you have no lineage preference, use Lahiri. It is the standard in Nepal and India and the value most published panchanga material follows.
3If you practise KP, use Krishnamurti. The method's tables and rules assume it.
4Never change it mid-case. A chart cast in one ayanamsha and transits read in another is an error you cannot see.
5Record which one you used. A chart without its ayanamsha cannot be reproduced or checked later.

In Jyotish Sarathi

Eleven or more ayanamsha systems are available, including Lahiri (Chitrapaksha), Raman and Krishnamurti, and the setting is in the Free plan rather than paywalled. Every chart reports the ayanamsha it was computed with, and that provenance is printed into the cheena. The methodology page documents where the tropical longitude comes from before the ayanamsha is subtracted.

Frequently asked questions

What is the ayanamsha value today?

For the Lahiri (Chitrapaksha) system it is a little over 24° in the mid-2020s, increasing by roughly 50 arc-seconds each year. Because it depends on the date, software computes it for the moment of the chart rather than using a stored figure.

Which ayanamsha is most accurate?

There is no astronomical test that settles it, because the question is where the sidereal zodiac is defined to begin, not where a physical object is. Lahiri is the most widely accepted and is India's official standard; Raman and Krishnamurti are internally consistent alternatives used by their own traditions.

Does ayanamsha matter more than the siddhanta?

Usually yes. Lahiri and Raman differ by around a degree and a half on every planet, which is larger than the typical disagreement between Surya Siddhanta and Drik Siddhanta.

Do Western astrologers use ayanamsha?

Most Western astrology is tropical, so it uses no ayanamsha at all. Western sidereal practitioners do, often with a Fagan-Bradley-style value that sits close to but not on the Lahiri figure.