Zodiac sign calculator
| Sign | Dates | Element | Quality |
|---|---|---|---|
| Aries ♈ | 21 Mar – 19 Apr | Fire | Cardinal |
| Taurus ♉ | 20 Apr – 20 May | Earth | Fixed |
| Gemini ♊ | 21 May – 20 Jun | Air | Mutable |
| Cancer ♋ | 21 Jun – 22 Jul | Water | Cardinal |
| Leo ♌ | 23 Jul – 22 Aug | Fire | Fixed |
| Virgo ♍ | 23 Aug – 22 Sep | Earth | Mutable |
| Libra ♎ | 23 Sep – 22 Oct | Air | Cardinal |
| Scorpio ♏ | 23 Oct – 21 Nov | Water | Fixed |
| Sagittarius ♐ | 22 Nov – 21 Dec | Fire | Mutable |
| Capricorn ♑ | 22 Dec – 19 Jan | Earth | Cardinal |
| Aquarius ♒ | 20 Jan – 18 Feb | Air | Fixed |
| Pisces ♓ | 19 Feb – 20 Mar | Water | Mutable |
Western astrology uses the tropical zodiac, fixed to the equinoxes rather than to the stars. Because the Earth axis precesses over about 26,000 years, the constellations have shifted roughly one whole sign since the dates were set two millennia ago, so someone born under "Aries" now has the Sun in front of Pisces. Astrologers are aware of this and consider it irrelevant to the system; astronomers consider it decisive. Both positions are internally consistent.
Astrology is a tradition, not a science. No study has found that a birth date predicts personality, or that two birth dates predict a relationship. This calculates what the tradition says, accurately.
Star signs follow the tropical zodiac: twelve bands of roughly thirty days, Aries from 21 March through to Pisces ending 20 March. Each sign carries an element, a quality and a ruling planet. Traditional compatibility is judged on those elements alone, which yields four possible scores rather than a measurement.
How to use the zodiac sign calculator
For anyone reading astrological writing, the element and the quality carry more than the sign name does, because they are what the tradition actually reasons with. Elements sort the signs into four temperaments; qualities sort them into three modes of acting. Together those give twelve unique pairings, which is exactly why there are twelve signs: four elements times three qualities, with nothing repeated.
The Sun sign is also the only part of a chart a date alone can produce. Moon sign, rising sign and house placements all need the time and place of birth too, since they depend on where the Earth was pointing at that moment. A horoscope written for a twelfth of the population is therefore the shallowest possible reading even on the tradition’s own terms, which is worth knowing before taking one personally.
Compatibility is shallower still. It reduces two people to one variable each and then to four element pairings, so the verdict has four possible values and the scheme holds nothing finer. A practising astrologer would run full synastry, the Moon, Venus and Mars placements and the aspects between two whole charts, and would treat sun-sign matching as close to meaningless. The popular version is what people look up, so it is the version this page reports. As evidence it stands nowhere: Shawn Carlson’s double-blind test in Nature in 1985 remains the cleanest of many that found nothing.
What people use it for
- Looking up a star sign from a birth date
- Getting the sign alone without the rest of the tradition
- Checking a cusp birthday against the boundary dates
- Reading the full table of sign dates, elements and qualities
- Comparing two birth dates on the traditional element scheme
- Settling an argument about what astrology actually claims
Questions
The chart under the panel lists all twelve, running from Aries on 21 March to Pisces ending 20 March. The exact boundary shifts by a day between years.
The Sun changes sign at a specific moment, so a birth time is needed for boundary dates.
In everyday use, yes. Both usually mean the sun sign — the zodiac sign the Sun occupied at birth.
Fire, earth, air or water: the tradition’s four temperaments, each covering three signs.
Cardinal, fixed or mutable — three modes of acting, each covering four signs. Some writers call it modality.
Traditionally those sharing an element, then fire with air and earth with water. Fire with water is the classic friction pairing.
No study has found any predictive value. This reports the tradition, not evidence.
Because the scheme is a lookup on four element pairings. There is no finer granularity in it.
Full synastry: Moon, Venus and Mars placements and the aspects between two whole charts, not sun signs.
The tradition says they complement each other. It also says a great many other things.
The constellations have, by about one sign since antiquity. Western astrology uses the tropical zodiac fixed to the seasons instead.
A thirteenth constellation the Sun passes through. It has never been part of the twelve-sign zodiac, which divides the year evenly rather than following constellation boundaries.
Moon sign, rising sign and planetary placements — all of which need a birth time and place, not the date alone.
By a day or so, because the Sun does not cross a boundary at the same clock time each year.