Western and Vedic astrology use the same twelve signs, each 30° wide, but they start the wheel from different points. The Western (tropical) zodiac starts at the spring equinox. The Vedic (sidereal) zodiac starts at a fixed point among the stars. The gap between the two starting points is the ayanamsa, and converting a position from one zodiac to the other is a single subtraction.
This guide works through that subtraction for real 2026 positions, shows which degrees change sign and which don't, and lists when the Sun enters each sign in both systems in 2026. Positions are AstroMystra's own calculation from the astronomy-engine ephemeris, with the Lahiri ayanamsa.
Two starting points
The tropical zodiac puts 0° Aries where the Sun is at the March equinox, when day and night are roughly equal. It is tied to the seasons: the Sun enters tropical Cancer at the June solstice every year.
The sidereal zodiac ties 0° Aries to the stars. Under the Lahiri convention, the reference star is Spica (Chitra), placed at 0° Libra; that is why Lahiri is also called Chitrapaksha.
The two starting points drift apart because Earth's axis slowly wobbles (precession), which moves the equinox backwards against the stars by about 50 arcseconds a year, roughly one degree every 72 years. Under Lahiri the two zodiacs coincided around the late third century CE. They are now a little more than 24° apart.
The ayanamsa in 2026
The Lahiri ayanamsa was 23°51′12″ on 1 January 2000 and grows by about 50″ a year. On 1 April 2026 it is 24°13′08″. AstroMystra's charts use this value; the Methodology page gives the formula and its source.
The conversion is:
- Sidereal longitude = tropical longitude − ayanamsa.
- If the result is negative, add 360°.
Worked example: Sun and Moon on 1 April 2026
The moment is 1 April 2026, 12:00 noon IST. Longitudes are measured from 0° Aries around the full 360° wheel, so 11°32′ Aries is 11°32′ and 1°57′ Libra is 181°57′.
- Step 1, the tropical positions: the Sun is at 11°32′36″ Aries (11.54°). The Moon is at 1°56′45″ Libra (181.95°).
- Step 2, subtract the ayanamsa: for the Sun, 11.54° − 24.22° = −12.68°, and adding 360° gives 347.32°. For the Moon, 181.95° − 24.22° = 157.73°.
- Step 3, read the sign: each sign is 30°, so divide by 30. 347.32° is in the twelfth sign (330–360°), Pisces, at 17°19′28″. 157.73° is in the sixth sign (150–180°), Virgo, at 7°43′36″.
So the Sun is in Aries in a Western chart and in Pisces (Meena) in a Vedic chart at the same moment. The Moon is in Libra in a Western chart and in Virgo (Kanya) in a Vedic chart.
When the sign stays the same
Not every position moves back a sign. On 18 April 2026 at noon IST the Sun is at 28°14′33″ tropical Aries. Subtracting 24°13′10″ leaves 4°01′22″, still Aries.
The rule follows from the subtraction. In 2026 the ayanamsa is about 24°13′, so:
- A tropical position from 24°13′ to the end of a sign stays in the same sign in the sidereal zodiac, about 24° lower.
- A tropical position below 24°13′ in a sign falls into the previous sign, at about 6° higher than its tropical degree (for example 11°32′ Aries becomes 17°19′ Pisces).
Because about 24 of every 30 degrees fall in the second group, most planets in a chart change sign between the two systems. A minority, in the last six degrees of a sign, keep it.
When the Sun enters each sign in 2026
The Sun moves about one degree a day, so a 24° offset becomes a gap of 24 or 25 days between the tropical and sidereal entry into the same sign. The dates below are AstroMystra's calculation in IST. The sidereal entries are the Sankrantis, so 14 January is Makar Sankranti and 14 April is Mesha Sankranti.
- Aries: tropical 20 March, sidereal 14 April
- Taurus: tropical 20 April, sidereal 15 May
- Gemini: tropical 21 May, sidereal 15 June
- Cancer: tropical 21 June, sidereal 16 July
- Leo: tropical 23 July, sidereal 17 August
- Virgo: tropical 23 August, sidereal 17 September
- Libra: tropical 23 September, sidereal 17 October
- Scorpio: tropical 23 October, sidereal 16 November
- Sagittarius: tropical 22 November, sidereal 16 December
- Capricorn: tropical 21 December 2025, sidereal 14 January
- Aquarius: tropical 20 January, sidereal 13 February
- Pisces: tropical 18 February, sidereal 15 March
Someone born on 1 April 2026 is an Aries by Western Sun sign and has the Sun in Meena in their Kundli. Vedic practice usually leads with the Moon sign (rashi) rather than the Sun sign; the Moon sign calculator gives the sidereal Moon sign from a birth date, time and place.
The Ascendant and houses
The same subtraction applies to the Ascendant, the degree rising on the eastern horizon at birth. A tropical Ascendant at 10° Leo becomes about 16° Cancer. Vedic charts then use whole-sign houses: the sign containing the sidereal Ascendant is the first house, the next sign the second, and so on. Western charts usually use a quadrant system such as Placidus. The Ascendant needs an accurate birth time, because it moves through a sign in about two hours.
Which zodiac is correct
Neither is a measurement error. They are two conventions that answer different questions: the tropical zodiac follows the seasons, and the sidereal zodiac follows the stars. Western astrology and Western Sun-sign horoscopes use the tropical zodiac; Jyotish, Kundli matching and Panchang use the sidereal one.
Within sidereal astrology there are also several ayanamsas. Lahiri is the one used by India's Rashtriya Panchang and most Vedic software; others, such as Raman and Krishnamurti (KP), differ from it by between a few arcminutes and about one and a half degrees. A planet within a degree or so of a sign boundary can land in a different sign under a different ayanamsa, so when two Vedic calculators disagree, compare the ayanamsa first.
Check your own chart
- Note a planet's tropical sign and degree from a Western chart.
- Subtract the ayanamsa for your birth year: about 23°51′ in 2000, 23°43′ in 1990, 24°13′ in 2026. The value grows by about 0°50′ every 60 years, so interpolate for other years.
- Read the new sign, then compare it with your Kundli.
AstroMystra's Kundli calculator gives sidereal positions with the Lahiri ayanamsa. The twelve signs themselves are described in The 12 Zodiac Signs, and What Is a Birth Chart explains how planets, signs and houses fit together.
Sources
- Lahiri ayanamsa values: the published historical table at Jagannatha Hora, from which AstroMystra's formula is derived (23.85333° on 1 January 2000, 0.0139289° a year).
- Planetary positions and Sun ingress dates: AstroMystra's calculation with the open-source astronomy-engine library; method on our Methodology page.