Zodiac sign calculator

What your zodiac sign is

Your zodiac sign (sun sign) is the part of the sky the Sun stood in on the day you were born. The sky along the Sun’s path is cut into twelve equal parts of 30° each, from Aries to Pisces. Western astrology and Indian (Vedic) astrology both use these twelve signs, but they start counting from different points, so the same birthday can give two different signs. This free tool shows both, worked out from the Sun’s real position for your birth year rather than from a fixed list of dates.

Western and Indian signs: why they differ

The Western (tropical) zodiac starts Aries at the spring equinox, the point where the Sun crosses the equator in March. The Indian (sidereal) zodiac starts Mesha from a fixed point among the stars. Because the Earth’s axis slowly wobbles, the equinox drifts backwards against the stars by about one degree every 72 years. Today the gap between the two zodiacs, called the ayanamsa, is about 24° (Lahiri ayanamsa, about 24.2° in 2026). That is why most people’s Indian sun rasi is one sign earlier: a Western Leo is usually an Indian Karka (Kadagam).

The Lahiri (Chitrapaksha) ayanamsa is the one adopted by the Calendar Reform Committee in 1955 and used in India’s national almanac (the Rashtriya Panchang, published by the Positional Astronomy Centre, Kolkata). This tool uses it too.

Sun rasi, moon rasi and nakshatra

When someone in Tamil Nadu asks “what is your rasi?”, they usually mean the moon rasi (Chandra rasi): the sign the Moon was in at your birth. The Moon moves about 13° a day and changes sign every two to two and a half days, so it needs your birth time. The nakshatra (star) divides the same circle into 27 parts of 13°20′, and each nakshatra into four padas of 3°20′. The nakshatra is what families use for naming customs and horoscope matching.

Turn on I know my birth time, type the hour and minute from the birth certificate and pick the time zone (all of India is UTC+5:30). Without a time, the tool still tells you the moon rasi or nakshatra when the Moon stayed in the same one all day.

Born on a cusp

Calendars print sign dates like “Leo: 23 July to 22 August”, but the Sun enters each sign at a different minute each year. If you were born on the day it changed sign, the tool says so and gives the exact time it moved; your birth time then settles which side you are on. The table shows the real dates for your own birth year.

How it’s worked out

1. The Sun’s position comes from the VSOP87 planetary theory (main terms, as given by Jean Meeus, Astronomical Algorithms, 2nd edition, 1998), accurate to about a second of arc between 1900 and 2100.
2. The Moon comes from the 60 main terms of Meeus, chapter 47.
3. The Western sign is the Sun’s longitude divided by 30°. The Indian rasi subtracts the Lahiri ayanamsa first.
4. The Tamil month of birth follows the Sun’s Indian rasi: Sun in Mesha is Chithirai, Karka is Aadi, Makara is Thai.

A story from Madurai

Meenakshi’s family in Madurai was choosing a name for her son, born on 26 January 1992 at 5:40 in the morning. A website said he was an Aquarius, and the family astrologer said Makara. Both were right: the Western sun sign is Aquarius, the Indian sun rasi is Makara (the Sun was in the month of Thai). With the birth time added, the tool also showed his moon rasi and nakshatra, which is what the family needed for the naming ceremony.

Matching two signs

Turn on Compare with a partner and pick their sign, or type their birthday. Tradition reads the distance between the two signs on the wheel: signs four apart share an element (a trine) and are said to get on easily; signs three apart (a square) are said to rub; opposite signs are said to attract. The tool names the relation in words and never gives a percentage, because tradition doesn’t.

Common mistakes

• Mixing up the two zodiacs. A newspaper horoscope uses the Western sign; a Tamil panchangam uses the Indian rasi.
• Using the sun rasi as “my rasi”. In India the moon rasi is usually meant.
• Guessing the birth time. Two hours can change the nakshatra; use the certificate.
• Forgetting summer time abroad. In London in July clocks are UTC+1, not UTC+0.