How does the zodiac sign calculator work?

It reads the month and day from your birth date and matches them against the 12 fixed tropical-zodiac boundary dates. Capricorn is the only sign that wraps over the year-end boundary (22 December to 19 January); all other signs fall within a single calendar month pair. No network request is made — the lookup happens instantly in your browser.

What is the tropical zodiac?

The tropical zodiac divides the ecliptic into 12 equal 30-degree segments anchored to the vernal equinox (around 21 March each year), not to the actual star constellations. It is the system used in Western astrology for sun-sign horoscopes. The sidereal zodiac, used in Vedic astrology, shifts those boundaries by roughly 23-24 degrees relative to the constellations.

What do the four elements mean?

Fire signs (Aries, Leo, Sagittarius) are associated with energy, passion and initiative. Earth signs (Taurus, Virgo, Capricorn) are linked to practicality, patience and stability. Air signs (Gemini, Libra, Aquarius) relate to intellect, communication and adaptability. Water signs (Cancer, Scorpio, Pisces) are connected to emotion, intuition and depth.

What is the quality or modality of a zodiac sign?

Each sign is one of three modalities. Cardinal signs (Aries, Cancer, Libra, Capricorn) initiate and lead. Fixed signs (Taurus, Leo, Scorpio, Aquarius) sustain and stabilise. Mutable signs (Gemini, Virgo, Sagittarius, Pisces) adapt and transform. Every element contains one of each modality, creating a 3x4 grid of 12 unique combinations.

My birthday falls on a cusp date — which sign am I?

The boundary between signs shifts by a day or two from year to year because the sun does not cross the ecliptic division at exactly midnight on the same calendar date every year. If your birthday is on or within one day of a boundary (for example 22 or 23 September), check an ephemeris or dedicated sun-sign lookup for your exact birth year to confirm whether the sun had already moved into the next sign by your birth time. This tool uses the conventional fixed-date boundaries that are correct for the majority of birth dates.

Is this the same as my sun sign?

Yes. In Western astrology the zodiac sign calculated from your birthday is your sun sign, which represents the position of the Sun in the ecliptic at the moment you were born. A full natal chart also includes a moon sign and a rising (ascendant) sign, which require the exact birth time and location to calculate.

Is my date of birth stored or shared?

No. The calculator runs entirely in your browser using local JavaScript. Your date is never uploaded to any server, logged or shared with any third party.

Zodiac Sign Calculator

Knowing your Western zodiac sign is as simple as knowing your birthday. Enter any date of birth and this calculator instantly returns your sign (Aries through Pisces), its element (Fire, Earth, Air or Water), its modality (Cardinal, Fixed or Mutable), its polarity and its ruling planet — the four axes that underpin Western astrological interpretation.

Everything is computed locally in your browser. No sign-up, no ads, no data sent anywhere.

How it works

The Western tropical zodiac divides the calendar year into 12 segments, each governed by a sign whose boundaries are fixed to specific calendar dates. The tool reads the month and day from your birth date and looks up which segment contains that date:

Sign	Dates
Aries	21 Mar – 19 Apr
Taurus	20 Apr – 20 May
Gemini	21 May – 20 Jun
Cancer	21 Jun – 22 Jul
Leo	23 Jul – 22 Aug
Virgo	23 Aug – 22 Sep
Libra	23 Sep – 22 Oct
Scorpio	23 Oct – 21 Nov
Sagittarius	22 Nov – 21 Dec
Capricorn	22 Dec – 19 Jan
Aquarius	20 Jan – 18 Feb
Pisces	19 Feb – 20 Mar

Capricorn is the only sign that crosses the year-end boundary, so the code handles it as a special case: any date from 22 December through 31 December, and any date from 1 January through 19 January, both map to Capricorn.

Once the sign is identified, the tool returns the four associated attributes that were established in classical Hellenistic astrology and have been used in Western horoscopy ever since.

The four axes explained

Element groups the 12 signs into four triplicities. Fire (Aries, Leo, Sagittarius) governs vitality and will. Earth (Taurus, Virgo, Capricorn) governs matter and practicality. Air (Gemini, Libra, Aquarius) governs intellect and relationship. Water (Cancer, Scorpio, Pisces) governs feeling and the unconscious.

Modality groups the signs into three quadruplicities. Cardinal signs open each season and are associated with initiative. Fixed signs hold the middle of each season and are associated with persistence. Mutable signs end each season and are associated with flexibility.

Polarity alternates sign by sign around the zodiac wheel. Positive (or masculine) signs — the six Fire and Air signs — are said to be outwardly expressive. Negative (or feminine) signs — the six Earth and Water signs — are said to be receptive.

Ruling planet is the classical celestial body most closely associated with a sign’s themes. Modern astrology adds the outer planets (Uranus for Aquarius, Neptune for Pisces, Pluto for Scorpio) as co-rulers alongside the traditional planets.

Worked example

Suppose you were born on 14 November. November 14 falls between 23 October (start of Scorpio) and 21 November (end of Scorpio), so the sign is Scorpio (symbol: ♏). Its element is Water, its modality is Fixed, its polarity is Negative (Feminine), and it is co-ruled by Pluto and Mars. The Fixed Water combination in classical interpretation is associated with deep emotional reserves, sustained focus and strong will.

Now try 22 December. That date is the first day of Capricorn (symbol: ♑), an Earth / Cardinal sign ruled by Saturn — associated with ambition, structure and long-term planning.