Zodiac Sign Lookup: Find Your Sign

A zodiac sign lookup tells you which of the 12 astrological signs you were born under, based on your birth date. You enter your date of birth, and you get back your Sun sign, the most commonly used sign in horoscopes. This article explains how the lookup works, what the signs and dates are, and how to handle edge cases like birthdays near a cusp.

Formula

The zodiac sign is determined by the day and month of birth. The formula is a simple date-range lookup:

• If (month = 1 and day ≥ 20) or (month = 2 and day ≤ 18) → Aquarius
• If (month = 2 and day ≥ 19) or (month = 3 and day ≤ 20) → Pisces
• If (month = 3 and day ≥ 21) or (month = 4 and day ≤ 19) → Aries
• If (month = 4 and day ≥ 20) or (month = 5 and day ≤ 20) → Taurus
• If (month = 5 and day ≥ 21) or (month = 6 and day ≤ 20) → Gemini
• If (month = 6 and day ≥ 21) or (month = 7 and day ≤ 22) → Cancer
• If (month = 7 and day ≥ 23) or (month = 8 and day ≤ 22) → Leo
• If (month = 8 and day ≥ 23) or (month = 9 and day ≤ 22) → Virgo
• If (month = 9 and day ≥ 23) or (month = 10 and day ≤ 22) → Libra
• If (month = 10 and day ≥ 23) or (month = 11 and day ≤ 21) → Scorpio
• If (month = 11 and day ≥ 22) or (month = 12 and day ≤ 21) → Sagittarius
• If (month = 12 and day ≥ 22) or (month = 1 and day ≤ 19) → Capricorn

Each sign spans roughly a month, but the start and end days vary slightly. The formula above uses the most widely accepted dates. In the calculator, the lookup(d, m) function applies these rules directly.

Worked Example

Using the default values: birth day = 15, birth month = 3 (March 15).

1. Check the March row: day ≥ 21? No (15 is less than 21).
2. Check the previous sign (Pisces): month = 3 and day ≤ 20? Yes, 15 ≤ 20.
3. Therefore, the sign is Pisces.

The calculator returns “Pisces” for March 15, which matches the date range for Pisces (Feb 19 – Mar 20).

How the Zodiac Sign Lookup Works

The lookup is based on the tropical zodiac, which divides the ecliptic into 12 equal 30° segments starting at the vernal equinox. Your Sun sign is the sign the Sun occupied at your birth. Because the Sun’s apparent path is regular, the dates are fixed each year (with a one-day shift in leap years for some signs, but the commonly used dates above ignore that minor variation).

There are 12 signs, each associated with an element (fire, earth, air, water) and a modality (cardinal, fixed, mutable). For example, Aries is a cardinal fire sign, Taurus is fixed earth, and Gemini is mutable air. These attributes are used in more detailed astrological interpretations.

How to Choose the Right Date Range

If your birthday falls on a date that is sometimes listed differently (e.g., some sources say Leo starts on July 23, others on July 24), use the date that is most common in modern Western astrology. The table below shows the standard date ranges:

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

If you were born on a cusp (e.g., March 20/21), you might want to check an ephemeris for your exact birth time and location, because the Sun’s entry into a sign can vary by a few hours.

Common Mistakes and Misconceptions

One common mistake is confusing the Sun sign with the rising sign (ascendant) or moon sign. The Sun sign is what most horoscopes use, but your complete birth chart includes all planets and points. Another mistake is using the wrong calendar: Western astrology uses the Gregorian calendar, not the lunar calendar. If you were born in a country that used a different calendar historically, you need to convert your birth date first.

Also, some people think the zodiac signs are tied to constellations, but the tropical zodiac is based on seasons, not the actual constellation positions. That’s why the dates are fixed and don’t match the astronomical constellations.

Limits of the Lookup

This lookup only gives your Sun sign. It does not account for the time of birth, which determines your rising sign, nor the positions of the Moon and planets. For a full natal chart, you need a professional astrologer or a dedicated astrology software. Also, the date ranges are approximate; the exact moment the Sun enters a sign varies by a few hours each year, so for a precise reading on a cusp birthday, you need an ephemeris.

Frequently Asked Questions

What if my birthday is on a cusp?

If you were born on the last day of one sign or the first day of the next, your sign depends on the exact time and time zone of your birth. For example, if you were born on March 20 at 11:00 PM, you might be Pisces, but if born on March 21 at 2:00 AM, you could be Aries. Use an online ephemeris or astrology calculator with your birth time to determine your exact sign.

Why do some sources give different dates for the same sign?

Different astrological traditions use different starting points. Western tropical astrology uses the vernal equinox, while sidereal astrology (used in Vedic astrology) uses the actual constellations, which shift over time. That’s why a person might have a different sign in Vedic astrology. The dates in this article follow the tropical system.

Does the zodiac sign change if I was born in a leap year?

No, the date ranges are the same every year. The Sun’s apparent position shifts by about one day every 128 years, but the fixed dates we use are a simplification. For a truly precise sign, you need the exact year and time.

Can I find my sign if I only know the year and month?

No, you need the day. The sign changes roughly every 30 days, so knowing only the month isn’t enough. For example, someone born in January could be Capricorn or Aquarius depending on the day.

Is the zodiac sign the same as the star sign?

Yes, “star sign” is a colloquial term for the Sun sign. It’s the sign the Sun was in at your birth, and it’s the most commonly referenced sign in daily horoscopes.

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in d | Birth day | day | 15 | 1
in m | Birth month | month | 3 | 1
out sign | Your zodiac sign | - | lookup(d, m) | 0