What is a birth chart?
A birth chart (natal chart) is a map of where the Sun, Moon and planets were in the zodiac at the exact moment and place you were born. Western astrology uses the tropical zodiac, anchored to the seasons, and reads each planet by its sign, its house (the area of life it colors) and its aspects (angles to other planets). Your Sun, Moon and Rising signs are the core of the chart.
How your chart is calculated
- 01Your birth time is converted to universal time using your birth city's time zone, including historical daylight saving.
- 02The Sun, Moon and all planets out to Pluto are calculated from astronomical ephemerides (VSOP87, ELP and Meeus), accurate to within about an arcminute.
- 03Your Ascendant and Midheaven come from the exact local sidereal time at your birthplace, and the twelve houses are divided with the Placidus system (Porphyry near the poles, where Placidus is undefined).
- 04Major aspects (conjunction, sextile, square, trine, opposition) are found between every pair of planets and angles, with slightly wider orbs for the Sun and Moon.
Sun, Moon and Rising: what's the difference?
| Point | What it describes | How often it changes sign |
|---|---|---|
| Sun sign | Your core identity, drive and sense of purpose | About once a month |
| Moon sign | Your emotions, instincts and what makes you feel safe | About every 2.5 days |
| Rising sign (Ascendant) | Your outward style and the first impression you make | About every 2 hours |
| Midheaven | Your public path, career and reputation | About every 2 hours |
Birth chart FAQ
Do I need my exact birth time?
For your Sun sign and most planets, the date is enough. Your Rising sign, Midheaven and house placements depend on the exact time: the Ascendant changes sign about every two hours, so a time off by an hour can change them. Your birth certificate is the best source.
How accurate is this chart?
Planet positions come from standard astronomical ephemerides and match published reference charts to within about an arcminute. Accuracy of the Rising sign and houses depends mostly on how accurate your birth time is.
What's the difference between Western and Vedic astrology?
Western astrology uses the tropical zodiac, tied to the seasons; Vedic astrology uses the sidereal zodiac, tied to the constellations. They currently differ by about 24 degrees, so your Vedic signs are usually one sign earlier. You can compare both on this site.
What are aspects?
Aspects are angles between planets. Trines and sextiles are usually harmonious, squares and oppositions bring tension that drives growth, and conjunctions blend two planets' energies. Tighter angles (smaller orbs) are felt more strongly.