Zodiac Sign Calculator

How to use the zodiac sign calculator

Enter your date of birth, then your time of birth and the city you were born in. Your sun, moon and rising signs appear at once, with the exact degree of each and the working underneath. If your town isn’t in the list, choose the nearest listed city in the same time zone, or switch to Enter coordinates and type the latitude and longitude (west and south are negative, or add W or S). No birth time? Leave it blank: you still get your sun sign, and usually your moon sign — the calculator checks whether either changed sign during that day.

Nothing is sent anywhere, and your birth details are not put in the page address, so the Share button shares the calculator, not your chart. This calculator is for entertainment; see the note on astrology and science below.

How your signs are calculated

Western astrology uses the tropical zodiac: the ecliptic — the Sun’s yearly path around the sky — divided into 12 equal 30° signs, starting from the point where the Sun crosses the celestial equator at the March equinox (0° Aries). A body’s sign follows directly from its ecliptic longitude λ:

• Sun. Instead of a fixed date table, the Sun’s apparent longitude is computed from the VSOP87 planetary theory as abridged by Jean Meeus in Astronomical Algorithms, corrected for nutation and aberration. It is accurate to about 1″, so the moment the Sun changes signs comes out within about a minute of the U.S. Naval Observatory’s equinox and solstice times.
• Moon. The Moon’s longitude comes from the 60 main periodic terms of Meeus’s lunar theory (a truncated ELP-2000/82), accurate to about 10″. The Moon moves about 13° a day, so when it is within 1° of a sign boundary the calculator shows the exact time it crossed, since a birth time that is off by an hour or two would change the sign.
• Rising sign. The ascendant is the point of the ecliptic on the eastern horizon. From the local sidereal time θ (the Greenwich sidereal time plus your longitude), the obliquity of the ecliptic ε and your latitude φ: ASC = atan2(cos θ, −(sin θ cos ε + tan φ sin ε)). A different sign rises about every two hours on average, faster or slower depending on the sign and your latitude.
• Time. Your local birth time is converted to Universal Time with the IANA time zone database built into your browser, which includes each region’s history of daylight saving time, wartime clock changes and local mean time before standard time zones.

Worked example

Take the example already in the calculator: born June 21, 1995 at 8:15 AM in New York. New York was on daylight time (UTC−4), so the birth was at 12:15 UT.

• Sun: apparent longitude 89.6690°, which is 29°40′ Gemini. Many date tables put June 21 in Cancer, but that day the Sun reached 90° — the June solstice and 0° Cancer — only at 4:34 PM EDT, so this person is a Gemini. Born that evening, they would be a Cancer.
• Moon: longitude 18.1493° = 18°08′ Aries, comfortably inside Aries.
• Rising: local sidereal time 18.9669°, obliquity 23.4376° and latitude 40.71° N give an ascendant of 124.1064° = 4°06′ Leo, so Leo rising. Leo was rising in New York from 7:54 AM to 10:27 AM that morning.

Zodiac sign dates

These dates were computed from the Sun’s position for every year from 1950 to 2049, in US Eastern Time. “Usual dates” are the most common first and last days, the next column shows how much the first day varies, and the 2026 column gives the exact moment the Sun enters each sign in 2026. In other time zones the change can fall on the day before or after.

Elements and modalities

Astrology groups the signs in two repeating patterns. The four elements cycle fire, earth, air, water from Aries, so each element has three signs, 120° apart. The three modalities cycle cardinal, fixed, mutable: the cardinal signs (Aries, Cancer, Libra, Capricorn) are the ones the Sun enters at an equinox or solstice, which is where the seasons begin in the Northern Hemisphere.

Signs, constellations and precession

The signs were named after constellations about two thousand years ago, when the March equinox point lay in the constellation Aries. Earth’s axis slowly wobbles (precession), moving the equinox west along the ecliptic by about 1° every 72 years, so today it lies in Pisces and the signs no longer line up with the star patterns of the same names. The tropical zodiac used here stays tied to the seasons; the sidereal zodiac of Vedic astrology stays tied to the stars, and the two now differ by about 24°.

Birth time and time zones

• Use the time on your birth certificate. Family memory is often rounded to the hour, which is enough to change a rising sign and, sometimes, the Moon.
• Daylight saving time is handled for you. If a clock time was skipped when clocks sprang forward, or happened twice when they fell back, the result says so.
• Older births: the time zone database is most reliable from 1970. For earlier dates it records the rules of each region’s main city, and some towns kept different time, so if your birthplace is far from the listed city, enter its coordinates and check its history.
• Near the poles (beyond 66° latitude) the ecliptic can lie almost flat along the horizon, so the calculator doesn’t give a rising sign there.

For other date questions, try the age calculator or the date difference calculator.

Astrology and science

Astrology is a centuries-old tradition that many people find meaningful or fun, but it is not supported by scientific evidence: the American Astronomical Society describes it as a belief rather than a science, and in a double-blind test published in Nature in 1985, astrologers could not match birth charts to personality profiles better than chance. Treat your signs as entertainment, not as advice for decisions about health, money or relationships. The positions of the Sun and Moon above are real astronomy, though — the same calculations are used to predict equinoxes and moon phases.