Calculate your free birth chart

A free birth chart, calculated from the real sky

A birth chart (also called a natal chart) is a map of where the Sun, the Moon and the planets were, as seen from the exact place and moment you were born. This free birth chart calculator works it out from your date, time and place of birth, draws the chart wheel and gives you a first reading of what each piece means.

It helps to keep two things apart. The calculation is astronomy: anyone using the same data and the same ephemeris should get the same positions to within a fraction of a degree. The reading is astrology: a symbolic language people use to reflect on temperament, motivation and the tensions they live with. We try to be precise about the first and honest about the second.

What goes into a natal chart calculation

Behind the wheel there are three separate steps, and each one can go wrong in a cheaper calculator.

1. Turning your birth time into universal time

Planet positions are calculated in universal time (UTC), so your local clock time has to be converted first. Time zones and daylight saving rules have changed many times in most countries, so we use the IANA time zone database, which records that history, so a birth in 1968 is converted with the rules that applied in 1968, not today's. The chart shows the offset we applied, so you can check it.

2. Planet positions

The positions of the Sun, Moon and planets come from NASA JPL's DE440 ephemeris, computed with the open-source Skyfield library. We use apparent geocentric positions in the tropical zodiac, where 0° Aries is the March equinox. The North Node is the true node. In our tests against Swiss Ephemeris, the planets agree to within two arc-seconds.

3. Rising sign, Midheaven and houses

The Ascendant, the Midheaven and the house cusps depend on local sidereal time, which is why they need an accurate time and place. The default house system is Placidus, the one most English-language astrologers learn first; you can also switch to whole sign, equal or Porphyry houses. Placidus breaks down near the poles, so for very high latitudes we fall back to Porphyry and tell you so. The full technical notes are on our methodology page.

Why your birth time matters so much

The planets move slowly enough that being a few hours off rarely changes their signs. The Moon is the exception: it moves about 13° a day and changes sign roughly every two and a half days. The sky's daily rotation is much faster still. The Ascendant moves through a whole sign in about two hours on average (less for some signs, more for others, depending on your latitude), and the house cusps move with it. A difference of fifteen minutes can be enough to move the rising sign or shift a planet from one house to the next.

If you only know your birth time roughly, choose the approximate option: we check an hour either side of the time you give and tell you which rising signs are possible within that window. If you don't know the time at all, we won't invent a rising sign or houses. We calculate the planets for local noon and tell you if the Moon might have been in either of two signs that day.

How to read your birth chart

A good birth chart reading builds up in layers rather than trying to take in everything at once.

• Start with the Big Three. Your Sun, Moon and rising sign give a first sketch: what drives you, what you need to feel settled, and how you meet the world. If that's all you want for now, the rising sign calculator gives you just those three.
• Read each planet as function, style and setting. The planet says what (Mercury is thinking and talking), the sign says how, and the house says where in life it tends to show up.
• Look at the tightest aspects. Aspects are angles between planets. A square or an opposition describes friction that tends to push for change; a trine describes ease. Neither is good or bad on its own. The closer an aspect is to exact, the more weight it usually gets.
• Look for repeated themes. One placement is a detail. The same idea showing up through three different routes is worth paying attention to.

Our step-by-step guide on how to read a birth chart goes into each of these, and the glossary explains terms like orb, cusp and chart ruler.

What's free and what the full report adds

The free chart gives you the interactive wheel, exact positions with degrees and minutes, your Big Three with interpretation, every planet read by sign, your four most significant aspects and your balance of elements.

If you want to go further, the full birth chart report reads every planet by sign and by house, interprets up to 24 aspects, and covers your chart ruler, Midheaven and North Node, as a web report and PDF you can keep. The personality profile organizes the same chart by theme instead. All reports and current prices are listed on the reports page, and members get some of them included: see membership.

Every interpretation is written in advance and assembled by fixed rules, so the same chart always produces the same text. It's meant as a starting point for reflection. It doesn't predict events and it isn't a substitute for medical, legal or financial advice.