Personal astrology tool · The Great Almanac
Zodiac Sign Calculator
The instrument
Natal Chart
Your personal reading
Natal ChartPreparing the instrument…
A birth date is all this needs, and the Sun’s place is worked out in your browser from the real solar longitude. Only a birth on the day the Sun changed sign needs more, and then the exact birth time settles which side of it you fell on.
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How the calculation works
Most sign tables round the boundaries, which is why two tables can disagree about a March 20th birthday. This tool computes the Sun's true ecliptic longitude for your birth moment using standard astronomical formulas (accurate to a fraction of a degree) and divides the circle into the twelve 30-degree signs starting at 0° Aries. Without a birth time it checks the whole day: if the Sun changed signs that day, it tells you so and asks for the time.
All twelve signs and dates
- Aries
- Mar 21 - Apr 19 · Fire · Cardinal · ruled by Mars
- Taurus
- Apr 20 - May 20 · Earth · Fixed · ruled by Venus
- Gemini
- May 21 - Jun 20 · Air · Mutable · ruled by Mercury
- Cancer
- Jun 21 - Jul 22 · Water · Cardinal · ruled by Moon
- Leo
- Jul 23 - Aug 22 · Fire · Fixed · ruled by Sun
- Virgo
- Aug 23 - Sep 22 · Earth · Mutable · ruled by Mercury
- Libra
- Sep 23 - Oct 22 · Air · Cardinal · ruled by Venus
- Scorpio
- Oct 23 - Nov 21 · Water · Fixed · ruled by Pluto
- Sagittarius
- Nov 22 - Dec 21 · Fire · Mutable · ruled by Jupiter
- Capricorn
- Dec 22 - Jan 19 · Earth · Cardinal · ruled by Saturn
- Aquarius
- Jan 20 - Feb 18 · Air · Fixed · ruled by Uranus
- Pisces
- Feb 19 - Mar 20 · Water · Mutable · ruled by Neptune
What this tool does
This calculator computes the Sun’s ecliptic longitude for your birth moment and returns your sun sign - with the exact degree when you add your birth time. On cusp days, the birth time settles the sign definitively.
Your sun sign is where the Sun actually stood on the day you were born. This calculator computes that position astronomically instead of reading a rounded date table.
Explore another reading
Continue with Natal Chart to add another perspective to your Almanac.
Open Natal ChartGo deeper
Common questions
Do I need my birth time?
Only if you were born on a cusp day. The calculator checks the Sun’s real position for your whole birth date; if the Sun changed signs that day, adding your time and time zone settles it exactly.
How accurate is the calculation?
It uses the standard low-precision solar position formulas from astronomical practice, accurate to a small fraction of a degree - far finer than the 30-degree width of a sign.
Is my sun sign my whole chart?
No. A full birth chart also places the Moon, rising sign, and planets in houses. The sun sign is the headline, not the whole story.
