What the Zodiac Moon Sign Calculator does
This calculator finds your Moon sign - the zodiac sign the Moon was in at the moment you were born - by computing the Moon's actual position from your birth date, local time and time zone. It gives the Western (tropical) sign and the Vedic rashi (sidereal, Lahiri), the nakshatra and its pada, and it warns you when the Moon changed sign on your birthday, which is the one case where the birth time decides the answer.
The Moon is the fastest-moving body in the sky. It covers about 13 degrees a day, so it spends only two to two and a half days in each sign, and a birth date on its own is not always enough. The position comes from the lunar theory in Jean Meeus's Astronomical Algorithms (the full table of 60 periodic terms), checked against NASA JPL Horizons. The calculation runs in your browser; your birth details are not sent anywhere.
How to use it
- Enter the birth date and the local clock time from the birth certificate or family records. If you do not know the time, tick "I don't know the time" and the tool uses noon and checks the whole day.
- Choose the time zone of the birthplace (for example Asia/Kolkata or Europe/London). The zone's own rules for that date are applied, including summer time and old historical offsets, so do not convert the time to UTC yourself.
- Read the headline: your Moon sign in the Western zodiac, with the degree. Below it is the sidereal rashi used in Indian astrology, the nakshatra and pada, and the Moon's phase.
- Check the panel under the headline. A green note means the Moon stayed in one sign all day. An amber warning gives the exact local time it moved into the next sign, so you can see which side of it you were born.
- Use the table to see when the Moon entered and left each sign in the days around the birth, and copy or download the result.
Reading the results
The tropical sign is the one Western horoscopes use; it is measured from the March equinox. The sidereal rashi is measured from a fixed point among the stars, and in 2026 the two differ by about 24 degrees (the ayanamsa), so the rashi is often the sign before your Western Moon sign. Neither is wrong - they are two conventions, and the page shows both so you can compare like with like.
If the panel says the Moon changed sign that day and you have no time, you genuinely have two possible Moon signs. A hospital record or a parent's memory of morning or evening is usually enough to settle it.
The degree tells you how close to a boundary the Moon was. At 29 degrees of a sign the Moon is about two hours from the next sign, so an uncertain birth time matters; at 15 degrees it does not.
The descriptive text is astrological tradition, not science. It is included because people ask what a Moon sign is said to mean, and it is labelled as convention, not as a measured fact about you.
Worked example: a morning birth in Mumbai
Born 15 August 1990 at 06:30 in Mumbai. India Standard Time is UTC+05:30, so the moment is 01:00 UTC on 15 August 1990, which is Julian day 2448118.5417.
The Moon's apparent longitude at that instant is 70.28 degrees. Each sign spans 30 degrees, and 70.28 / 30 = 2.34, so it is in the third sign, Gemini, at 70.28 - 60 = 10.28 degrees, written 10 deg 16' Gemini.
The Lahiri ayanamsa that day is 23.73 degrees, so the sidereal longitude is 70.28 - 23.73 = 46.55 degrees: 16 deg 33' of the second sign, Taurus, which is Vrishabha rashi. 46.55 / 13.333 = 3.49, so the Moon is in the fourth nakshatra, Rohini, in its second pada.
The Moon entered Gemini on 14 August at 13:11 and left it on 16 August at 15:42 local time, so the whole birth day sits inside Gemini and the exact time does not change the answer.
Formulas and scoring rules
- Moment of birth
UTC = local clock time - zone offset on that date; JD = Unix ms / 86,400,000 + 2,440,587.5The offset comes from the browser's IANA time-zone database, so summer time and historical changes are applied. Terrestrial Time adds Delta T (about 69 seconds in 2026) from the Espenak-Meeus polynomials.- Moon longitude
lambda = L' + sum of 60 terms l_i x sin(a_i D + b_i M + c_i M' + d_i F) + additive terms + nutationMeeus, Astronomical Algorithms, chapter 47. L' is the Moon's mean longitude, D the mean elongation, M and M' the Sun's and Moon's mean anomalies, F the argument of latitude. Accuracy about 10 arc-seconds.- Sign
sign index = floor(lambda / 30); degree in sign = lambda - 30 x indexIndex 0 is Aries, 11 is Pisces.- Sidereal (Lahiri)
lambda_sid = lambda - ayanamsa; ayanamsa = 23 deg 15' 00.658" on 21 March 1956 + general precession since thenThe definition used by the Indian Astronomical Ephemeris, carried forward with the IAU 2006 precession rate of about 50.3 arc-seconds a year.- Nakshatra and pada
nakshatra = floor(lambda_sid / 13.3333) + 1; pada = floor(remainder / 3.3333) + 1Twenty-seven equal divisions of 13 deg 20', each split into four padas of 3 deg 20'.
Why the birth time matters for the Moon and hardly at all for the Sun
The Sun moves about one degree a day, so it changes sign only twelve times a year and your Sun sign is safe unless you were born on a cusp day. The Moon moves about thirteen times faster. It changes sign every 54 to 60 hours, which means that on roughly two days in every five the change happens at some hour during the day. On those days a morning and an evening birth have different Moon signs.
The time zone matters for the same reason. A birth at 23:30 in New York is already the next morning in London and in India, and the Moon has moved about six degrees in that half day of clock difference. Entering the local time with the local zone avoids that mistake.
Western Moon sign or Vedic rashi?
Western astrology ties the signs to the seasons: 0 degrees Aries is where the Sun crosses the equator in March. Vedic astrology ties them to the stars, and because the equinox slowly drifts westward against the stars (precession, about one degree every 72 years), the two zodiacs have separated by roughly 24 degrees today. When people in India ask for a moon sign or rashi, they mean the sidereal one; most Western horoscope columns mean the tropical one.
Limitations: what the result does not prove
- The astronomy is accurate to well under a minute of arc, but the answer is only as good as the birth time you enter. Recorded birth times are often rounded to the nearest five or fifteen minutes.
- Historical time zones depend on the browser's time-zone database. For births before about 1970 in places whose clocks changed often, check the offset shown under "Time used" against a local record.
- Only the Lahiri ayanamsa is offered for the sidereal zodiac. Other ayanamsas (Raman, Krishnamurti) differ from it by up to about 1.5 degrees, which can change a rashi when the Moon is near a boundary.
- The meanings shown are astrological tradition. They are not a scientific description of personality and should not be used to make decisions about health, money or relationships.
Privacy: where your data goes
Everything you paste, type or drop is processed in this browser tab. It is not uploaded, logged, stored or sent to analytics. Session recording and tag-manager scripts are switched off on this page.
Standards and sources
- NASA JPL Horizons - solar system ephemeris used to check positions - checked 19 Sep 2026
- Paul Schlyter - How to compute planetary positions
- NASA Eclipse Web Site - Delta T polynomial expressions (Espenak and Meeus)
- IANA Time Zone Database
Frequently asked questions
How do I find my Moon sign by date of birth?
Enter the date, the local time and the time zone of the birthplace. The tool computes where the Moon actually was at that instant and divides the zodiac into twelve 30-degree signs. If you leave the time out, it checks the whole day and tells you whether the Moon changed sign.
Can I find my Moon sign without a birth time?
Often, yes. The Moon spends about two and a half days in each sign, so on most dates it stays in one sign for the whole day and the time does not matter. When it changed sign during your birthday, the tool shows both signs and the exact changeover time so you can narrow it down.
Is the rashi the same as the Moon sign?
The rashi is the Moon sign in the sidereal zodiac used in Indian astrology. It is measured from the stars rather than the equinox, so it is usually one sign earlier than the Western Moon sign. The page shows both, with the Lahiri ayanamsa used for the difference.
Why does another website give me a different Moon sign?
Usually because one site uses the sidereal zodiac and the other the tropical, or because a time zone or summer-time offset was applied differently. Compare the degree and the zodiac type: two sites using the same zodiac and the correct time should agree to within a fraction of a degree.
What is a nakshatra and pada?
Nakshatras are the 27 lunar mansions of Indian astrology, each 13 degrees 20 minutes of the sidereal zodiac, and each is divided into four padas of 3 degrees 20 minutes. Your birth nakshatra is the one the Moon occupied, and it is used for naming and for traditional compatibility matching.
How accurate is the Moon position?
The lunar series from Meeus is accurate to about 10 arc-seconds, and the tests compare it with NASA JPL Horizons at eight dates between 1912 and 2088. That is far finer than the half-degree the Moon covers in an hour, so the birth time is always the larger source of error.
Does my Moon sign change if I was born during summer time?
The sign does not change, but the clock time does. Choosing the birthplace time zone applies the summer-time offset in force on that date automatically. If you convert the time yourself and also pick the zone, you would subtract the hour twice.
Last reviewed by the A2Z.Tools team against the sources listed above.
