What Is a Birth Chart?

Q: What is a birth chart?

A birth chart, or natal chart, is a map of where the Sun, Moon and planets stood at the exact moment and place you were born. It places them in the twelve signs of the zodiac and the twelve houses, the areas of life, and shows the angles between them. Astrologers read it as a picture of your nature - the energies you carry and how they tend to work together.

Most people meet astrology through a single word: their sign. "I'm a Scorpio." It is a fair place to start, and it is about a tenth of the story. That word names where the Sun was on the day you were born. At the same moment, the Moon was somewhere, Mercury, Venus and Mars were somewhere, and a particular point of the zodiac was rising on the eastern horizon where you were born. A birth chart is the full picture of all of that.

A snapshot of the sky

Imagine standing where you were born, at the minute you were born, and looking up. The Sun, the Moon and the planets are spread across the sky along one narrow band, the path the Sun appears to travel over a year. Astrology divides that band into twelve equal parts, the signs of the zodiac, and notes which sign each planet was in.

It also notes the horizon. Part of the sky was rising in the east, part was setting in the west, part stood overhead. Those positions turn the snapshot into something personal. Two people born on the same day in different cities, or a few hours apart in the same city, share most of their planets' signs and still have different charts.

1The signs, the twelve parts of the Sun's path
2The houses, the sky around the birthplace, as twelve areas of life
3The planets, where each one stood at birth
4The Ascendant, the sign rising in the east

A birth chart is drawn as a wheelHuman Design Zone

The chart is drawn as a wheel because the sky is round. Earth is at the centre, which is where we see the sky from. The outer ring holds the signs, the inner ring holds the houses, and the planets sit where they were.

The three building blocks

Almost everything in a chart comes from three things working together.

The planets are the energies. The Sun is your sense of self, the Moon your emotional needs, Mercury your mind, Venus what you love, Mars your drive, and so on. See the planets.
The signs are the styles. A planet in a sign takes on that sign's way of acting: Mars in Leo acts boldly, Mars in Virgo acts precisely. See the signs.
The houses are the areas of life: self, money, home, partnership, career and the rest. A planet's house shows where its energy plays out. See the houses.

Then come the aspects, the angles between planets, which show how those energies talk to each other: easily, with friction, or by merging. See aspects.

If you remember one line, remember this: the planet says what, the sign says how, the house says where. The next article, Planet, Sign and House, shows how to read any placement that way.

What you need to calculate a chart

Three pieces of information:

Your date of birth. This places the Sun and the faster planets.
Your place of birth. This sets the horizon you were born under.
Your time of birth, as exact as you can find it. Birth certificates, hospital records and family memory are the usual sources.

The time matters more than most people expect. The whole wheel of houses turns once a day, so a new sign rises roughly every two hours on average, and the house a planet falls in can change within minutes. The Moon also moves quickly, crossing a whole sign in about two and a half days, so on some days the birth time decides the Moon's sign too.

Without a time, a chart is still useful. The planets' signs and most of the aspects are known. What you lose are the houses, the rising sign and the angles, the most personal layer.

You can create your own natal chart in a couple of minutes.

Which zodiac?

Western astrology, and everything on this site, uses the tropical zodiac. Its signs are measured from the spring equinox, so they stay tied to the seasons: 0 degrees Aries is always the start of spring in the northern hemisphere. The constellations that gave the signs their names have slowly drifted away from them over the centuries, so the sign and the constellation of the same name no longer line up. That is expected, not an error. Indian (Vedic) astrology uses a different, star-based zodiac, which is why its signs are often one sign earlier.

Today the spring equinox, 0 degrees of the sign Aries, falls in the constellation Pisces, and the constellation Aries begins about 29 degrees into the sign Aries.

Signs twelve equal 30-degree parts of the Sun's path, counted from the spring equinox
Constellations star groups of unequal size, drifting with precession
Ophiuchus the thirteenth constellation on the Sun's path, never a sign
Spring equinox 0 degrees Aries, where the sign zodiac begins

The signs follow the seasons; the constellations have driftedHuman Design Zone

See your own birth chart

Every sign, planet and house you just read about, placed exactly as the sky stood when you were born.

Create your Natal Chart Free, takes 2 minutes

What a chart can and cannot tell you

A chart describes energies and the way they tend to combine. It can show what comes easily to you, where you are pushed to grow, what you need to feel safe, how you love and how you act under pressure. It can help you understand why you and someone close to you keep meeting in the same places.

A chart does not decide your life. The same placement can be lived in a hundred ways, from its gifts to its shadow, and the difference is awareness and choice. Read it as a description of the instrument you were born with, not a script for the music.

That is also why nothing in a chart is good or bad. A placement that asks more of you often becomes your greatest skill.