Free astrology calculator
Birth Chart Calculator
Enter your date, time and place of birth. Your chart is calculated in your browser from an astronomical ephemeris, with the historical time zone of your birthplace applied, and every placement comes with a short, careful interpretation.
How this birth chart is calculated
Planet positions come from Astronomy Engine, an open-source astronomical library accurate to about one arcminute. We tested this calculator against the Swiss Ephemeris, the reference used by professional astrology software, on eight charts from 1879 to 2024 across both hemispheres: every planet, angle and house cusp agreed to within half an arcminute.
The birth time is converted to Universal Time using the historical time zone rules of your birthplace, including daylight saving time as it was observed that year. For births before standard time zones were adopted, we use the local mean time of the city itself, the same convention used by major astrology references. The resolved offset is shown with your result so you can check it.
Signs use the tropical zodiac. Houses default to Placidus; near the poles, where Placidus cannot be calculated, we switch to Porphyry and say so. If you do not know your birth time, we leave out the rising sign and houses, which depend on it, and tell you whether the Moon changed sign that day. More detail on our methodology page.
To compare your chart with someone else's, the synastry chart calculator sets two charts side by side and lists the aspects between them; our guide to synastry explains how astrologers read them. If the wheel is new to you, start with how to read a birth chart.