A birth chart, also called a natal chart, is a map of the sky as it looked from the exact place and moment you were born. It records where the Sun, the Moon and the planets stood along the zodiac, which part of the zodiac was rising over the eastern horizon, and how all of those points were angled to each other. The positions themselves are astronomy and can be calculated precisely for any date in history. The meanings layered on top come from a long interpretive tradition, and astrologers read the chart as a symbolic portrait rather than a set of instructions. This guide explains each part of the wheel and then walks through reading one, step by step.
Seen from Earth, the Sun appears to travel a fixed path through the stars over the course of a year. That path is called the ecliptic, and the Moon and planets always stay close to it. Astrology divides the ecliptic into twelve equal slices of 30 degrees each: the twelve zodiac signs. A birth chart is essentially a list of where every planet sat along that 360-degree circle at your birth, for example "Venus at 14 degrees Scorpio."
Three pieces of information are needed. The date places the Sun and the slower planets. The time places the fast-moving Moon and, more importantly, fixes which sign was on the eastern horizon. The place matters because the horizon is local: at the same instant, a person born in Seoul and a person born in Chicago see completely different parts of the sky rising and setting. That is why two people born on the same day can have quite different charts. For more on this, see why birth time matters.
Most charts are drawn as a circle with the twelve signs around the outer ring. The horizontal line through the middle is the horizon. The point on the far left, where the eastern horizon meets the zodiac, is the Ascendant, or rising sign. Directly opposite on the right is the Descendant, where the zodiac was setting. Near the top sits the Midheaven (MC), the highest point the zodiac reached overhead, and at the bottom is the IC, the point directly beneath your feet.
The chart reads counterclockwise from the Ascendant, and it is oriented the way you would see the sky facing south from the Northern Hemisphere. This gives the wheel an intuitive logic. Someone born around sunrise will have the Sun close to the Ascendant on the left. Someone born around noon will have it near the top. Someone born at midnight will find it near the bottom, below the horizon line, because the Sun really was on the other side of the Earth. Each planet appears as a small symbol (a glyph) with its exact degree beside it.
A simple working rule: the planet is what is being described, the sign is how it expresses itself, and the house is where in life it tends to show up.
Now combine. Mars is drive; Gemini is a quick, curious, talkative air sign. So Mars in Gemini tends to read as someone who fights with words, argues for the fun of it and runs several projects at once. The shadow side of the same placement is scattered energy and starting more than gets finished. Put Mars in Taurus instead and the drive becomes slow, steady and very hard to push off course. You can read more about each planet in the planets guide and about each sign on its own page, such as Gemini or Taurus.
The twelve houses divide the wheel into areas of life, starting from the Ascendant and running counterclockwise:
Venus in the 10th house, for example, suggests that love of beauty or a gift for diplomacy may show up in public work. There are several ways of dividing the houses. Placidus is common in modern Western astrology, Whole Sign houses are used in Hellenistic and Vedic astrology, and Equal houses are a simpler alternative. They agree on the broad picture but can move a planet from one house to the next. Houses depend on the exact birth time. The houses guide covers them in depth.
Aspects are specific angles between two planets, measured along the zodiac. The five major ones are:
Planets rarely sit at the exact angle, so astrologers allow an orb, a margin of a few degrees. Many use around 6 to 8 degrees for the major aspects and a little more when the Sun or Moon is involved. The tighter the orb, the louder the aspect. A Moon square Saturn, for instance, is often read as feelings that were kept in check early on, and a person who can become very dependable for others while learning, slowly, to let themselves be looked after. See the aspects guide for the full set.
A quick worked example: Sun in Aries, Moon in Cancer, Virgo rising, with Mercury as chart ruler in Pisces. This person may lead with a careful, helpful manner (Virgo), act boldly when something matters (Aries), and need a secure home base to recharge (Cancer), while thinking in images and intuitions more than lists (Mercury in Pisces). Notice how the Aries Sun and Cancer Moon square each other: independence and the need for closeness pull in different directions, and learning to honor both is part of the story.
Reading one placement in isolation. A single "difficult" placement never defines a chart. Every piece is modified by the others.
Treating squares and oppositions as bad. Tension is often where motivation comes from. Many capable people have charts full of squares.
Treating the chart as a forecast. A birth chart describes tendencies and themes. It does not decide what you will do, and it works best as a prompt for reflection.
Mixing up systems. Western astrology uses the tropical zodiac, tied to the seasons, while Vedic astrology uses the sidereal zodiac, tied to the stars. The two currently differ by about 24 degrees, so the same person can have different signs in each. The Western vs Vedic guide explains the difference.
If you know your birth date, time and place, you can see your own birth chart on My Stella, drawn over a rebuilt view of the actual sky at that moment. Without a birth time, the rising sign and houses are left out rather than guessed.
Your date of birth, time of birth and place of birth. The date and place are enough for the planets' signs, but the time is needed for the rising sign, the houses and sometimes the Moon's sign.
Yes. Birth chart, natal chart and nativity all refer to the same thing: the map of the sky at the moment of birth.
Only if they were born at nearly the same minute in nearly the same place. Twins born some minutes apart can already show a different Ascendant degree or house placements, and the rising sign changes roughly every two hours.
No. The natal chart is fixed at the moment of birth. What changes is the current sky, and astrologers compare the moving planets to your natal chart to talk about transits and timing.