Birth chart calculator (natal chart)
A birth chart, or natal chart, is a map of where the Sun, Moon and planets were along the zodiac at the exact moment and place you were born. To calculate it you need your birth date, the birth time (as exact as possible) and the town of birth. Without a birth time you still get planet signs, but not the Ascendant or houses.
Showing an example (1 Jan 2000, 12:00, London). Enter your details to reveal yours.
- Trine
- Sextile
- Square
- Opposition
| Planet | Position | Sign | House | Motion |
|---|---|---|---|---|
| Midheaven | 9°30′ | Capricorn | 10 | |
| Ascendant | 24°01′ | Aries | 1 | |
| Sun | 10°22′ | Capricorn | 10 | |
| Moon | 13°19′ | Scorpio | 7 | |
| Mercury | 1°53′ | Capricorn | 9 | |
| Venus | 1°34′ | Sagittarius | 8 | |
| Mars | 27°58′ | Aquarius | 12 | |
| Jupiter | 25°15′ | Aries | 1 | |
| Saturn | 10°24′ | Taurus | 1 | ℞ retrograde |
| Uranus | 14°48′ | Aquarius | 11 | |
| Neptune | 3°12′ | Aquarius | 11 | |
| Pluto | 11°27′ | Sagittarius | 8 | |
| North Node | 3°57′ | Leo | 5 | ℞ retrograde |
| Chiron | 11°37′ | Sagittarius | 8 |
- Updated
- How we calculate it
- Computed on your device
Enter your date, time and place of birth to see your chart wheel, a table of planet positions in degrees, your houses and the main aspects between planets. Every placement links to a short, plain-English explanation.
Don't know your birth time? Leave it empty. We show what is certain (most planet signs) and flag what depends on the time – for example if the Moon changed sign on your birthday.
Your planets, sign by sign
How we calculate it
Planet positions come from Astronomy Engine, an open-source astronomy library (MIT license) whose author documents an accuracy of about ±1 arcminute. We use apparent geocentric positions on the true ecliptic of date (IAU 2006 precession and IAU 2000B nutation, with light-time and aberration) – the same definition most astrology software uses.
Your local birth time is converted to Universal Time with the historical rules of the IANA time zone database, including past daylight-saving changes and war-time clocks. City coordinates and time zones come from GeoNames. If a time was skipped or repeated because the clocks changed, we tell you instead of guessing silently. One honest limit: for births before about 1970 the database is not guaranteed to be complete, and a small town may have kept a different local time than the reference city of its zone. We always show the UTC offset we applied, so you can compare it with what you know (for example a time on a birth certificate).
We test the engine against NASA/JPL Horizons (DE441) for reference birth data: planets agree within 1 arcminute and the Moon within 2; the Ascendant and Midheaven, computed from Horizons sidereal time, agree within 3 arcminutes.
Everything runs in your browser. Your birth data is not sent to a server and nothing is stored.
House systems and zodiac
The default house system is Placidus, the most common in modern Western astrology. You can switch to Whole Sign, Equal or Koch. Close to the poles, Placidus and Koch cannot be computed; there we fall back to Porphyry and say so.
Positions use the tropical zodiac (signs measured from the March equinox). A sidereal option (Lahiri ayanamsa) is available for Vedic-style comparisons.
How accurate does my birth time need to be?
Planet signs rarely depend on the minute, but the Ascendant moves about one degree every four minutes on average, and house cusps move with it. A time from a birth certificate or hospital record is far more reliable than a remembered "around noon". When a point is within 1° of a sign boundary, we warn you.
What is in a birth chart?
Planets (Sun to Pluto, plus the lunar North Node and Chiron) show what kind of energy is described. Signs describe how that energy tends to express itself. Houses show which area of life it is linked with, and aspects are the angles between planets – how the parts of the chart talk to each other.
The Sun, Moon and Ascendant are often called your "Big Three" and are the usual starting point for reading a chart.
Questions
What do I need to calculate my birth chart?
Your date of birth, the time of birth and the place (city or town). The place gives the coordinates and the historical time zone, which are needed to turn your local clock time into Universal Time.
Can I get a birth chart without a birth time?
Yes. Planet signs are mostly the same all day, so you still get them. The Ascendant, Midheaven and houses need the time, and the Moon can change sign during the day – we show whether that happened on your date.
What's the most accurate natal chart calculator?
Accuracy comes from three things: a good ephemeris, correct historical time zones and an accurate birth time. Our positions are tested against NASA/JPL Horizons to within arcminutes; the biggest remaining source of error is usually the recorded birth time.
Which house system should I use?
Placidus is the most widely used in Western astrology and is our default. Whole Sign houses are popular in traditional and Hellenistic astrology. There is no single correct system – they are different conventions.
Can ChatGPT explain my birth chart?
A chatbot can describe what placements traditionally mean, but language models are not ephemerides and can get positions wrong. Calculate the chart with an astronomical tool first, then read the interpretations.
Sources
- Astronomy Engine (Don Cross) – source code and documentation, MIT license
- NASA/JPL Horizons System – reference ephemerides used to test our results
- IANA Time Zone Database (tz database) – historical time zone and daylight-saving rules
- IANA tz database – theory and accuracy of historical data
- GeoNames geographical database (CC BY 4.0) – city coordinates and time zones
- IAU SOFA – standards of fundamental astronomy (IAU 2006 precession, IAU 2000B nutation)
- NASA GSFC – Polynomial expressions for Delta T (Espenak & Meeus)
- Astro-Databank – birth data with Rodden accuracy ratings
Astrology, numerology and the Chinese zodiac are offered for entertainment and self-reflection. They are not scientifically validated and are not a substitute for professional advice (medical, psychological, legal or financial). Astronomical positions are calculated precisely; interpretations are traditional symbolism, not predictions.