Birth Chart Calculator

What is Online Birth Chart Calculator?

Birth Chart Calculator draws your natal chart: a map of the sky at the moment and place you were born. Enter your birth date, time and town, and it works out where the Sun, the Moon and the planets stood in the zodiac, which sign was rising on the eastern horizon, and how the twelve houses fall. You get the chart wheel, your Big Three (Sun, Moon and rising sign), every planet’s sign, degree and house, the aspects between them, and a plain-English reading.

Everything is calculated in your browser with a modern astronomical ephemeris, accurate to well under an arcminute, the same precision as the big astrology sites. Your birth details are never sent anywhere. The time zone, and whether daylight saving time was in force, is looked up for your birthplace on your birth date, back to the local mean time used before time zones.

A natal chart wheel with signs, houses, planets and aspect lines, and a story image with the Sun, Moon and rising sign

What You Get

• Chart wheel: signs, houses, planets with their degrees, and colour-coded aspect lines, in a cosmic, light or print theme.
• Big Three: your Sun, Moon and rising sign at a glance, with what each means.
• Planets and houses: each planet’s exact position, house and retrograde motion, plus the Ascendant, Midheaven and every house cusp.
• Aspects: conjunctions, sextiles, squares, trines and oppositions, with their orbs.
• Element and modality balance: how much fire, earth, air and water, and cardinal, fixed and mutable, your chart holds.
• Five house systems: Placidus, Whole Sign, Equal, Koch and Porphyry.
• Tropical or sidereal: Western astrology, or the Vedic zodiac with the Lahiri ayanamsa.
• Downloads: the chart as a PNG, a Big Three story image to share, a PDF report, and a link that opens the same chart.

How to use Online Birth Chart Calculator?

1. Enter your birth date and the time on the clock where you were born.
2. Start typing your birthplace and pick it from the list.
3. Choose a house system and the tropical or sidereal zodiac if you like.
4. Read your Big Three, planets, aspects and reading, then download the chart or share the link.

Frequently asked questions

What is a birth chart?

A birth chart, or natal chart, is a snapshot of the sky from where you were born, at the moment you were born. It places the Sun, the Moon and the planets in the twelve signs of the zodiac and in twelve houses, each for an area of life. Astrologers read it as a map of your personality and potential.

What are my Big Three?

Your Sun sign (your “star sign”, about who you are at the core), your Moon sign (your emotions and needs) and your rising sign, or Ascendant (how you come across and meet the world). The Sun sign only needs your birth date; the Moon needs the day, and the rising sign needs the exact time and place.

Why does the birth time matter?

The rising sign changes about every two hours, and the house cusps move a degree every four minutes, so the time decides your Ascendant, Midheaven and which house each planet falls in. The Moon also moves about 13° a day. If you don’t know your time, tick “I don’t know my birth time”: you still get the planets in their signs, charted for noon, and the Moon’s sign is flagged if it changed that day. A birth certificate or a hospital record often has the time.

Which house system should I choose?

Placidus is the most widely used in Western astrology and the default here. Whole Sign, where each house is one whole sign starting from the rising sign, is the oldest and popular in Hellenistic and Vedic astrology. Equal houses are 30° each from the Ascendant. Koch and Porphyry are other quadrant systems. Near the poles, Placidus and Koch cannot be drawn, so Porphyry is used instead.

What is the difference between tropical and sidereal?

Tropical astrology, used in the West, starts the zodiac at the spring equinox. Sidereal astrology, used in Vedic (Jyotish) astrology, ties it to the stars. Because of the precession of the equinoxes the two are now about 24° apart, so in the sidereal zodiac most placements move back one sign. The sidereal option here uses the Lahiri ayanamsa, the standard in India.

Is this birth chart calculator accurate?

Yes. Planet positions come from the astronomy-engine ephemeris and agree with the Swiss Ephemeris, which most astrology software uses, to well under an arcminute; the houses follow the standard formulas. Most differences between sites come from the birth time, the time zone or the house system. Places come from GeoNames (CC BY 4.0), with every town of 5,000 people or more; for a smaller place, choose the nearest town or enter its coordinates.

Are my birth details private?

Yes. The chart is calculated on your device and nothing is sent to our servers. Your last chart is kept in your browser so it is there when you come back, and a shared link holds the birth details in the link itself. For more cosmic fun, make a Life in Weeks Calendar from your birth date, or explore the Solar System Simulator.