Zodiac Sign Calculator
Your Western zodiac sign from your birth month and day.
Quick answer
- Formula: Sign = the zodiac span containing the month/day, using the standard tropical cusp dates (Aries from March 21, etc.)
- Worked example — Zodiac sign: Aries (full example below).
Zodiac Sign Calculator
| Zodiac sign | Aries |
| Date range | March 21 – April 19 |
| Symbol | ♈ |
March 21 is the first day of Aries ♈, which runs from March 21 to April 19.
Enter a birth month and day to find the Western (tropical) zodiac sign, its date range and its traditional symbol.
Signs change on fixed calendar dates called cusps, so only the month and day matter — the birth year is not needed for the Western zodiac (it is needed for the Chinese zodiac).
The formula
Worked example
March 21 is the first day of Aries ♈, which runs from March 21 to April 19.
The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.
Frequently asked questions
What if my birthday is on a cusp?
This calculator uses the most widely published cusp dates. Some almanacs shift a cusp by a day in certain years because the Sun's exact entry moment varies — if you were born on a boundary day, your sign can depend on the year and time of birth.
What about February 29 birthdays?
February 29 falls within Pisces (February 19 – March 20), and the calculator accepts it.
Is Ophiuchus a zodiac sign?
Not in the traditional twelve-sign system used here. The constellation Ophiuchus crosses the ecliptic, but the astrological zodiac has kept twelve signs of 30° each.
Category: Date & Time calculators
Sources & methodology
This calculator applies the formula shown on this page exactly as written, using the standard definitions for its inputs. Results are computed from the values you enter — no data is stored — and are rounded only for display.
Content last reviewed by CalcHub Editorial.
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