Birth chart guidesThe basics
What is a birth chart?
By the Hourwyn team
A birth chart, also called a natal chart, is a diagram of where the Sun, the Moon and the planets were in the sky at the exact time and place a person was born. Astrologers read it as a description of character. Making one takes three facts: a birth date, a birth time and a birthplace.
What a birth chart shows
The chart is a circle that stands for the sky as seen from the birthplace, with Earth at the center. Four layers are drawn on it.
| Layer | What it is | How many |
|---|---|---|
| Planets | The Sun, the Moon and the eight planets from Mercury to Pluto. Astrology calls all ten of them planets. | 10 |
| Signs | Twelve equal slices of the Sun's yearly path, 30 degrees each, from Aries to Pisces. | 12 |
| Houses | Twelve sections of the sky set by the time and place of birth. Each is tied to an area of life. | 12 |
| Aspects | Angles between two planets, such as 90 degrees (a square) or 120 degrees (a trine). | 5 major |
Many charts also mark the lunar node, the point where the Moon's path crosses the Sun's. Each layer has its own guide: the Big Three signs, the twelve houses and the aspects.
What you need to make one
- Birth date. It sets the sign of the Sun and of the slower planets.
- Birth time. It sets the rising sign and all twelve houses. The rising sign moves about one degree every four minutes, so the time matters more than most people expect.
- Birthplace. It sets the latitude and the time zone. The same clock time in New York and in Los Angeles is three hours apart in the sky.
A chart can still be made when the time is unknown, with limits. See what a chart can show without a birth time.
Birth chart, natal chart, horoscope: are they the same?
Birth chart and natal chart are two names for the same thing. Natal means "of birth". In older books the chart itself is called a horoscope. Today a horoscope usually means the short sun sign forecast in a magazine or an app, which uses one of the ten planets: the Sun. A birth chart uses the whole sky, which is why two people with the same sun sign can have very different charts.
How a chart is put together
- The birth time is converted from local clock time to universal time, using the time zone and daylight saving rules in force at that place on that date.
- The positions of the Sun, Moon and planets at that instant are taken from an ephemeris, a set of positions computed from models of the solar system.
- The rising sign and the houses are worked out from the time and from the latitude and longitude of the birthplace.
- The angle between every pair of planets is measured, and the pairs that sit close to an aspect are listed.
The full method, with the sources we use, is in how a birth chart is calculated.
What a birth chart cannot tell you
The positions on a chart are astronomy, and they can be checked. What they are said to mean is astrology, a tradition of interpretation more than two thousand years old. Controlled studies have not found that birth charts predict personality or events, which we cover in is astrology accurate. A chart is best read as a set of themes to think about. It does not forecast your future, and it is no basis for a medical, financial or legal decision.
Common questions
Is a birth chart the same as a zodiac sign?
No. Your zodiac sign, or sun sign, is one item on the chart: the sign the Sun was in when you were born. The chart also holds the Moon, eight planets, twelve houses and the angles between them.
Does a birth chart change over time?
No. It is fixed to the moment of birth. What moves is the present-day sky, and astrologers call the comparison between the two "transits".
Can two people have the same birth chart?
Only if they were born at the same minute in the same place. Twins born a few minutes apart have nearly identical charts, because the rising degree shifts by about one degree every four minutes.
How much does a birth chart cost?
On Hourwyn the chart itself is free with an account, and no card is needed. The written Personality Report built on that chart is a single payment of $19, with no subscription.
See it on your own chart
Enter a birth date, time and place and we calculate the wheel, every placement and every aspect. Free with an account. No card needed.
Keep reading
Sources
- What's the difference between astrology and astronomy?. NASA Space Place.
- Time Zone Database. Internet Assigned Numbers Authority (IANA).
The guides are written by Hourwyn with the help of AI tools. Astronomical and historical facts are checked against the sources listed under each guide. Astrology is described as a tradition and offered for entertainment. Nothing here is medical, financial, legal or psychological advice.