Free birth chart calculator
Planetary positions computed from a VSOP87 / lunar ephemeris for your exact date, time and coordinates. Tropical zodiac, Placidus houses.
Calculate to draw the wheel — signs, houses, and the gold glyphs for your planets.
How a birth chart is calculated
A natal chart is a diagram of the sky from one place at one moment. Two inputs do the work: time, which fixes where each body sat along the ecliptic, and coordinates, which fix which part of that sky was rising. SideraChart resolves the birthplace to latitude and longitude, converts local clock time to Universal Time with the IANA timezone rules in force on that date, then reads planetary longitudes from a VSOP87-class ephemeris (astronomy-engine).
Positions are given in the tropical zodiac, measured from the vernal equinox — the Western convention. Sidereal longitudes differ by roughly 24° today and are not shown in this calculator.
Why birth time matters
The Ascendant moves about one degree every four minutes, so a twenty-minute error shifts it by five degrees and can change the sign entirely. The Moon moves roughly half a degree an hour. Sun through Pluto are stable enough across a day that an unknown time still gives a usable chart, minus the houses.
House systems
Placidus is the default because it is the most widely used, and most published interpretations assume it. It divides time rather than space, which makes houses uneven and breaks down above roughly 66° latitude; for births in the far north, Whole Sign is the more honest choice.