Birth chart calculator
Enter date, time, and birth coordinates. Computes ascendant, midheaven, planet positions in the tropical zodiac, whole-sign house placements, and major aspects. Birth data stays in your browser.
About this calculator
Planetary positions are computed with Astronomy Engine (MIT-licensed VSOP87 + ELP-2000). Ascendant and midheaven are derived from local sidereal time and the mean obliquity of the ecliptic at the birth instant.
Houses default to Whole-Sign - the Hellenistic convention where each house corresponds exactly to one zodiac sign, starting from the ascendant's sign. Placidus, the standard quadrant system, is also available from the house-system selector; its intermediate cusps are solved iteratively from each point's diurnal semi-arc, falling back to whole-sign for circumpolar cusps at extreme latitudes. See methodology for the trade-offs.
Aspects are major (conjunction / opposition / trine / square / sextile) and minor (semisextile / semisquare / sesquiquadrate / quincunx / quintile / biquintile), with classical orbs from cited sources.
Questions
- What do I need to enter to get a birth chart?
- A birth date, a clock time, and a place. Picking a city fills in latitude, longitude, and the UTC offset that applied on that date, including daylight saving. You can also type coordinates and the offset in minutes yourself, for example -300 for US Eastern Standard Time.
- How much does the birth time matter?
- The ascendant moves through all twelve signs in about a day, roughly one degree every four minutes, so the ascendant, midheaven, and every house placement depend on the minute. The Moon moves about one degree every two hours. Sun through Pluto sign placements usually survive an error of an hour or two unless the body is close to a sign boundary.
- Why does my chart differ from another site?
- The usual causes are the house system, the time zone, and the zodiac. This calculator defaults to whole-sign houses and offers Placidus; many sites default to Placidus. It uses the tropical zodiac, so a sidereal (Vedic) chart will show most placements one sign earlier. A wrong UTC offset for the birth date shifts the ascendant by about 15 degrees per hour.
- Which aspects are listed, and how tight do they have to be?
- Five major aspects (conjunction, opposition, trine, square, sextile) and six minor ones. Each aspect has a default orb; minor aspects are allowed 60% of theirs. An aspect within one degree of exact is marked as exact in the table.
- Is my birth data stored?
- No account, no database. The chart is computed by JavaScript in your browser. If you copy the page link to share a chart, the date, time, and coordinates are written into that link, so share it only with people you would tell those details to.
Reference, not advice
This is cultural and astronomical reference, not personal prediction or advice.
This calculator is a reference tool. Astrology is documented cultural and historical material; it is not a scientifically demonstrated method of prediction. See the disclaimer.
Last reviewed .