ONE QUESTION · A WORKED CHART

What is Lahiri ayanamsa?

By Esha · Example dated

Subtracting a fixed 24° is a rough shortcut; using Lahiri ayanamsa means applying an offset calculated for the date. Ayanamsa is the angular gap between two zodiac starting points: tropical, based on the March equinox point, and sidereal, tied to a stellar reference. Lahiri is a widely used Indian convention for that gap, which became the standard for Indian sidereal calendars through the Calendar Reform Committee's work in 1955, as the Swiss Ephemeris documentation explains.

The convention takes its name from N. C. Lahiri. Two calculations can both be labelled Vedic while using different reference settings, such as Lahiri or Raman. The setting affects the coordinates used to assign signs and birth-star divisions. Compare it before assuming the date or time was entered incorrectly. When comparing tropical and sidereal numbers, use the same birth instant and the same method for calculating the Moon's position.

See it in a chart

Example birth: 15 January 1990, 08:30 IST · New Delhi

For the fictional birth on 15 January 1990, the matching tropical Moon is at 162.796059°. Subtract the applied Lahiri offset of 23.721451° and the sidereal result is 139.074608°, in Leo and Purva Phalguni, its nakshatra or birth-star division. Leo's ruler is the Sun; Purva Phalguni's period lord is Venus, which starts the dasha, or planetary-period schedule. Both the Sun and Venus sit in Capricorn in the first house with Rahu in this chart. The setting therefore connects to several labels and their interpretation, rather than only changing the word beside the Moon.

Birth date
15 January 1990
Applied Lahiri offset
23.721451°
Matching tropical Moon
162.796059°
Lahiri sidereal Moon
139.074608°

For your own chart

Match the birth inputs and ayanamsa when comparing charts, then compare the Moon's degree, sign and birth star. Use unrounded values for subtraction. Near a boundary, a small difference may change the sign or pada, meaning quarter. Even away from a boundary, a degree difference changes the starting period balance.

Six decimal places make the arithmetic easier to follow; they do not make an approximate birth time exact.

For astrologers: calculation details

Fictional Demo Chart A · 15 January 1990, 08:30 IST (UTC+05:30)
New Delhi, India; 28.6139° N, 77.2090° E

Lahiri sidereal zodiac; mean nodes; whole-sign houses; geocentric geometric positions; Vimshottari with a 365.25636-day year. UTC birth instant: 1990-01-15T03:00:00Z. Reference instant: 2026-09-28T06:30:00Z.

Angles are rounded to six decimal places; arithmetic uses the saved full values. Period boundaries are displayed to the nearest second in IST. These settings describe the calculation, not the precision of a birth record.

Follow the calculation

  1. Start from the matching geometric tropical longitude, 162.796059°. Keep the birth instant fixed.
  2. Subtract the applied Lahiri offset of 23.721451° for that instant. The result is 139.074608° in the sidereal zodiac.
  3. Use the unrounded values for subtraction and sign selection. Six decimal places here are a display choice, not a statement that the model or birth record is perfect to that precision.

Sources

How Esha checks its calculations