What is a birth chart?

A birth chart is a map of the sky at the moment you were born, drawn for the place you were born in. It shows where the Sun, the Moon and each of the planets stood, which signs they were in, and how the sky was turned in relation to the horizon at that minute. It is also called a natal chart; the two names mean the same thing. Every reading starts from it, and nothing about it changes across a life. It is the one fixed moment the rest of astrology is measured against.

A chart can look like a diagram meant for someone else: a circle cut into wedges, scattered with symbols and crossed with lines. Once you know what its parts do, though, it reads more like a paragraph about a person. This guide covers what goes into one, how the wheel is laid out, and a practical order for reading your own.

What you need to cast a chart

Three pieces of information go into a birth chart, and each one does a different job.

Your date of birth places the Sun and most of the planets. The Sun stays in one sign for about a month and the slower planets for much longer, so the date alone settles a good deal.

Your place of birth matters because the sky looks different from different points on Earth. The same moment seen from Manila and from London usually puts a different sign on the eastern horizon.

Your time of birth sets the Rising sign and the houses. As the Earth turns, a new sign rises over the eastern horizon roughly every two hours, and all twelve houses turn with it. A birth time out by an hour can move the Rising into the next sign and shift every planet into a different house, while the planets' signs stay exactly the same. That is why it is worth finding the recorded time rather than a guess, if you can.

If you do not know your birth time, you can still cast a chart. The free birth chart calculator has an option for an unknown time. You get the signs of the Sun and planets and most of the relationships between them. What you cannot get is a reliable Rising sign or houses. On a day when the Moon changed signs, its sign may also be uncertain without a time.

The four working parts

A chart is built from four kinds of thing, and each answers a different question.

The signs are the twelve familiar names, Aries through Pisces. They describe style: how something is done. Charm and Soul uses the tropical zodiac, which is tied to the seasons of the year rather than to the fixed stars. Each sign belongs to one of four elements and one of three modalities, which the primer on elements and modalities explains.

The planets are the moving bodies, and each one is a function in a life. The Sun is identity and purpose. The Moon is feeling and need. Mercury is thought and speech, Venus is love and value, and Mars is drive. Jupiter and Saturn describe growth and structure, and the slow outer planets describe changes that unfold over years. The planets primer takes each one in turn.

The houses are twelve areas of life, such as money, home, partnership and work. If a planet is the actor and its sign is the way it acts, the house is the setting where the action happens. Charm and Soul draws houses in the Placidus system, one of the most widely used house systems in Western astrology. The twelve houses walks through all of them.

The aspects are the angles planets form with one another. Two planets in aspect are in conversation, sometimes cooperating and sometimes pulling against each other. Aspects are what turn a list of placements into a person with tensions and gifts. The guide to astrological aspects describes the major ones.

How the wheel is laid out

A Western chart wheel is drawn as if you were looking south from your birthplace, with the eastern horizon on the left. That left-hand point, level with the middle of the circle, is the Ascendant, where the Rising sign sits. Directly opposite, on the right, is the Descendant, the western horizon.

The houses are numbered counterclockwise from the Ascendant. The first house starts at the Ascendant and runs downward, below the horizon line, and the numbers continue round the bottom of the wheel, up the right-hand side and across the top. The point at the top of the chart is the Midheaven, the highest part of the sky at your birth, which begins the tenth house.

This layout carries information on its own. Planets in the lower half of the wheel were below the horizon when you were born, and planets in the upper half were above it. A Sun in the lower half means a birth between sunset and sunrise, and a Sun in the upper half means a daytime birth.

The inner part of the wheel usually shows the aspects as lines between planets. Around the edge sit the sign symbols, and each planet is placed by its position in its sign.

Reading your chart, step by step

You do not have to read every symbol at once. The order below starts with the placements that say the most and works outward.

Step one: the Sun, Moon and Rising

Three placements carry most of the weight, so start there. The Sun is the self you are growing into and the purpose you organise a life around. The Moon is your inner life: what you feel, what you need and what comforts you. The Rising sign is how you meet the world, the manner people see before they know you. Read their signs first, then notice how well they fit together. A chart whose three pillars share an element tends to feel consistent from the inside. One whose three pillars pull in different directions tends to hold more inner conversation. The primer on Sun, Moon and Rising goes further into each.

Step two: the chart ruler

The planet that rules your Rising sign is called the chart ruler, and it acts as a kind of guide for the whole chart. If you have Libra rising, Venus is your chart ruler; with Aries rising, it is Mars. For Scorpio, Aquarius and Pisces rising, astrologers read the traditional ruler (Mars, Saturn and Jupiter), and many also look at the modern one (Pluto, Uranus and Neptune). Find the chart ruler in your chart and notice its sign and house. The area of life it sits in often becomes a steady theme across a life.

Step three: the balance of elements and modalities

Count where your planets fall by element and by modality. A chart heavy in fire leans toward action and enthusiasm, one heavy in earth toward the practical and the steady, air toward ideas and connection, water toward feeling and intuition. A missing element is worth noticing too. It rarely means a lack. More often it marks something you learn deliberately instead of by instinct.

Step four: where the planets gather

Look at which houses hold the most planets. A cluster of planets in one house, sometimes called a stellium, shows the area of life where much of your energy goes. Empty houses are normal, since there are more houses than main planets. An empty house is not an empty part of life. Its affairs are read through the sign on its cusp and the planet that rules that sign.

Step five: the aspects

Start with aspects to the Sun, the Moon and the chart ruler, since these colour the placements you have already read. A harmonious aspect, such as a trine, describes parts of you that work together easily. A challenging one, such as a square, describes a friction that tends to push you to grow. Neither kind is good or bad on its own terms. A chart with demanding aspects is often a chart with a great deal of drive, because friction gives a person something to work against.

Step six: the finer points

Once the main structure is clear, the chart has more to offer. The lunar nodes describe a direction of growth across a life, which the guide to the North and South Node explains. Retrograde planets, marked with a small R, work in a more inward way. Chiron and Black Moon Lilith add their own themes. These are best read after the foundations, not before.

Putting it together

The hardest and most interesting part of reading a chart is holding its contradictions. A fiery Sun can sit over a watery Moon. A reserved Rising can hide a very expressive chart ruler. These are not errors. A person is not one thing, and a chart that shows tension between placements is describing something real about how that person lives.

The skill is weighing. A placement repeated in several ways, say a strong Scorpio Sun, a Pluto on the Ascendant and planets in the eighth house, is saying the same thing three times, and deserves more weight than a single aspect standing alone.

A chart drawn and a chart read

A free calculator draws the chart: the signs, the houses and the aspects, laid out as a wheel or a table. That data is accurate and it is where every reading begins. On its own, though, it does not interpret. It tells you where everything is without telling you what the pattern means in your life.

A chart reading is that interpretation. It weighs the placements against one another, notices which themes repeat, and describes the chart as one shape instead of a list of parts. It is only as good as the chart beneath it, and the chart is only as good as the birth details it was cast from, which is why the time and place matter so much.

Starting with your own

The simplest way to learn a chart is to look at your own while you read about it. Cast your free birth chart with the most accurate time you can find, then take the steps above one at a time. Begin with the Sun, Moon and Rising, find your chart ruler, and see where your planets gather. The rest of the wheel becomes easier to read once those are clear.