What is a birth chart?

A birth chart is the exact representation of the position of the planets in the sky at the precise moment of your birth. Unlike a daily horoscope, it is unique to each person: two individuals born on the same day, but a few hours apart or in two different cities, will have different birth charts.

How is a birth chart calculated?

The calculation relies on three precise pieces of information: your date, time, and place of birth. Based on this data, the exact position of every planet in the solar system (from the Sun to Pluto) in the sky is determined, as well as two essential axes: the Ascendant and the Midheaven.

It is this combination of precise astronomical data that makes each chart unique. The time of birth plays a particularly important role: a difference of just a few minutes can change your Ascendant sign, and therefore alter part of the interpretation.

What a birth chart reveals

A complete birth chart is organized around three families of elements, which combine to create a detailed portrait:

The planets — each one represents a dimension of your personality: the Sun your identity, the Moon your emotions, Mercury your communication, and so on.
The zodiac signs — they indicate how each planet expresses itself.
The astrological houses — they specify in which area of your life (love, career, family...) this energy manifests concretely.

Taken in isolation, a sun sign tells only a tiny fraction of the story. It is the combination of these elements, related to one another, that gives a birth chart all its richness.

A concrete step-by-step example

The chart of Julie, born May 14 at 8:12 AM in Lyon

Let's take a simple example to illustrate how a birth chart is read.

Julie's simplified birth chart, calculated for May 14, 1990 at 8:12 AM in Lyon: the 12 houses (outer circle), the 12 zodiac signs (middle circle), and her 10 planets. Tap or hover over a symbol to see its name.

Her Sun is in Taurus, in her 12th House (the unconscious): her stable identity, rooted in the concrete, expresses itself mostly in her inner world, away from the public eye, rather than through public self-assertion.

Her Moon is in Capricorn, in her 7th House (partnerships): her emotional needs are expressed through a need for structure and seriousness in the way she relates to others.

Her Ascendant, calculated using her precise birth time (8:12 AM), is in Gemini: she projects a curious, communicative, and adaptable image—this is also what marks the beginning of her 1st House, the house of identity.

The Ascendant is also what determines the placement of all the houses in the chart: once its position is fixed, the other eleven houses follow one another around the circle from this point, with sizes that vary depending on the houses—which explains why the wheel is not divided into twelve equal parts.

We also notice that several planets are grouped in Capricorn in her chart (the Moon in the 7th House, Uranus and Neptune also in the 7th House, and Saturn just next to it in the 8th House): this is called a stellium, a reinforcement of the influence of this sign and these houses on her personality—here, everything relating to partnerships and deep transformations.

Even with just these three elements, a coherent portrait begins to emerge—much richer than just the "Taurus" label from her daily horoscope. A complete chart like the one we calculate for each Astrabook takes into account all the planets, houses, and the aspects between them to further refine this reading.

What's your chart?

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Date of birth

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Place of birth

These 3 keys are just a preview — discover your full chart in your Astrabook.

Why is every birth chart unique?

The sky is constantly changing: the Moon changes signs about every two days, and the houses shift over the hours with the Earth's rotation. This is why even twins born a few minutes apart can have a different Ascendant, and therefore a significantly different chart.

This precision is also what distinguishes a personalized birth chart from a generic horoscope: it is intended for only one person, at a unique and non-reproducible moment.

Frequently asked questions

Can you calculate your birth chart without knowing your time of birth?

Yes, but the analysis will be less precise: without an exact time, it is impossible to determine the Ascendant and the houses with certainty. The Sun, Moon, and other planets, however, can still be calculated from the date alone.

Does a birth chart change over the course of life?

The natal chart itself remains fixed: it corresponds to a precise moment and never changes. However, the planets continue their path in the sky after birth, which creates interactions with the natal chart—this is what we call transits.

Is a birth chart the same thing as an astrological chart?

Yes, these are two terms for the same thing: the representation of the position of the celestial bodies at a given time and place. "Birth chart" and "natal chart" are the terms most commonly used in astrology.