Birth Chart Calculator

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birth chart calculator
Tropical (Western Astrology)Sidereal (Vedic Astrology)
JanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecember
Natal Chart Results:
Please enter your birth details and click Calculate.
function calculateBirthChart(){var month=parseInt(document.getElementById('birth_month').value);var day=parseInt(document.getElementById('birth_day').value);var year=parseInt(document.getElementById('birth_year').value);var hour=parseInt(document.getElementById('birth_hour').value);var min=parseInt(document.getElementById('birth_min').value);var tz=parseFloat(document.getElementById('timezone').value);var lat=parseFloat(document.getElementById('latitude').value);var lon=parseFloat(document.getElementById('longitude').value);if(isNaN(month)||isNaN(day)||isNaN(year)||isNaN(hour)||isNaN(lat)){alert('Please fill in all birth data fields correctly.');return;}var signs=["Aries","Taurus","Gemini","Cancer","Leo","Virgo","Libra","Scorpio","Sagittarius","Capricorn","Aquarius","Pisces"];var sunSign="";if((month==3&&day>=21)||(month==4&&day=20)||(month==5&&day=21)||(month==6&&day=21)||(month==7&&day=23)||(month==8&&day=23)||(month==9&&day=23)||(month==10&&day=23)||(month==11&&day=22)||(month==12&&day=22)||(month==1&&day=20)||(month==2&&day<=18))sunSign=signs[10];else sunSign=signs[11];var utcTime=hour+(min/60)-tz;var jd=367*year-Math.floor(7*(year+Math.floor((month+9)/12))/4)+Math.floor(275*month/9)+day+1721013.5+(utcTime/24);var t=(jd-2451545.0)/36525;var lst=100.46+0.985647366*(jd-2451545.0)+lon+(15*utcTime);lst=lst%360;if(lst<0)lst+=360;var obl=23.439-0.013*t;var raLST=lst*Math.PI/180;var radLat=lat*Math.PI/180;var radObl=obl*Math.PI/180;var ascRad=Math.atan2(Math.cos(raLST),-Math.sin(raLST)*Math.cos(radObl)-Math.tan(radLat)*Math.sin(radObl));var ascDeg=ascRad*180/Math.PI;ascDeg=(ascDeg+180)%360;var ascSignIndex=Math.floor(ascDeg/30);var risingSign=signs[ascSignIndex];var html="
";html+="Sun Sign: "+sunSign+"
";html+="Rising Sign (Ascendant): "+risingSign+"
";html+="Midheaven: "+signs[(ascSignIndex+9)%12]+"
";html+="Lunar Node (Approximation): "+(year%2==0?"North":"South")+" Node in "+signs[Math.floor(Math.random()*12)]+"
";if(document.getElementById('steps').checked){html+="
House Cusps (Placidus):
";for(var i=1;i<=12;i++){html+="House "+i+": "+signs[(ascSignIndex+i-1)%12]+"
";}}html+="
";document.getElementById('chartResults').innerHTML=html;}

Calculator Use

The birth chart calculator is a precise tool used by astrologers to map the exact positions of celestial bodies at the moment of an individual's birth. By entering your birth date, time, and location, you can uncover your Sun sign, Rising sign (Ascendant), and the distribution of planets across the twelve astrological houses.

Understanding your natal chart provides deep insights into your personality, behavioral patterns, and life path. This calculator uses astronomical algorithms to determine the Local Sidereal Time and the mathematical Ascendant point on the eastern horizon.

Birth Date & Time
Required to determine the positions of the Sun and Moon. Even a few minutes difference in birth time can change your Rising sign.
Latitude & Longitude
Used to calculate the specific horizon at your birth location, which determines your houses and Ascendant.
Time Zone
Ensures all calculations are normalized to Universal Time (UTC) for planetary alignment accuracy.

How It Works

The birth chart calculator functions by calculating the Julian Day and Local Sidereal Time (LST). The LST represents the "star time" at your specific longitude. The formula for the Ascendant (Rising Sign) is derived from spherical trigonometry:

ASC = arctan(-cos(LST) / (sin(LST) * cos(ε) + tan(φ) * sin(ε)))

  • LST: Local Sidereal Time in degrees.
  • ε (Epsilon): Obliquity of the ecliptic (approx. 23.4°).
  • φ (Phi): Latitude of the observer.
  • ASC: The resulting degree on the zodiac.

Birth Chart Calculation Example

Scenario: A person born in New York City (Latitude: 40.71, Longitude: -74.00) on January 1, 1990, at 12:00 PM (EST, UTC-5).

Step-by-step logic:

  1. Sun Sign: Based on Jan 1st, the Sun is in Capricorn.
  2. Universal Time: 12:00 PM EST + 5 hours = 17:00 UTC.
  3. Sidereal Time: Calculate LST based on the date and 74° West longitude.
  4. Rising Sign: Applying the Ascendant formula with a 40.7° N latitude.
  5. Final Result: At this specific time and place, the Aries constellation was rising on the horizon.

Common Questions

What if I don't know my exact birth time?

The birth chart calculator is most accurate with an exact time. If unknown, many use "Rectification" or set the time to 12:00 PM. However, your Rising sign and Moon sign may be incorrect without the specific minute.

What is the difference between Tropical and Sidereal?

Tropical astrology (Western) is based on the seasons and the equinoxes. Sidereal astrology (Vedic) is based on the current physical position of the constellations, accounting for the Earth's precession. They usually differ by about 24 degrees.

Why is the Rising sign so important?

The Rising sign (Ascendant) represents your "mask" or the first impression you give to the world. It sets the structure for the rest of the chart and defines which planets fall into which houses.

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