The exact sky you were born under.

Positions come from the Swiss Ephemeris, an astronomical library used by professional astrology software, working from your birth moment converted to Universal Time. The Sun, Moon and planets are geocentric ecliptic longitudes of date. The North Node and Lilith are mean points, the convention most astrology sites follow. Houses are Placidus or Whole Sign, as you choose, and Placidus falls back to Whole Sign near the polar circles where it is undefined.

Your birth time is local clock time, and clocks have not always matched today's. The calculator looks up the offset that was in force at your birthplace on your birth date, including daylight saving, using the IANA time zone database, then convert to Universal Time. The note under the chart shows exactly what was applied. Records before 1970 are less certain for some regions, so for an early birth it is worth checking the offset against a document.

The same engine was run over a large set of simulated birth moments, drawn from births between 1950 and 2024 using assumed seasonal and time-of-day curves (not fitted to real birth records) and places weighted by city population, and counted how often each placement and combination occurs. “0.6% of charts” means that share of the simulated births had it, and “1 in 150” is the same figure turned around. The ranking says where it sits among every possible sign or combination, always from the nearer end: “33rd rarest of 144” or “26th most common of 144”. Ties are called ties, and in the big groups (144 Sun and Moon pairs, 1,728 big threes) neighboring ranks differ by less than the simulation’s own sampling noise, so those ranks are given as “about” and “1 in N” is rounded to the digits the count can support. Because it is a count of people born in those years, a slow planet is common when a whole generation shares its sign: Pluto in Scorpio is not rare, it is the 1984 to 1995 cohort. The number of simulated births is shown with each chart. The simulation measures tropical placements, so for a sidereal chart the rarity shown is for the tropical signs, and the page says so. It is a count of how often something happens, not a judgement of what it means.

The Rising sign changes about every two hours and the houses turn with it, so without a time they are left out rather than guessed. The Moon moves about 13 degrees a day, so for an unknown time the chart is calculated for noon and the Moon's sign can be wrong by up to roughly half a day of travel. The Sun and the slow planets barely change.

Tropical, the default, measures the zodiac from the March equinox and is what Western astrology uses. Sidereal measures from the fixed stars using the Lahiri ayanamsa and is what Vedic astrology uses, which moves most points back about 24 degrees. The planets do not move; only the signs they are counted in do. Placidus divides the houses by time and Whole Sign gives each sign one house. Switch any of them above and the chart recalculates.

Genastro does not keep your birth details. They are sent to the server to calculate the chart and are not saved. The share link holds the chart in the part of the address after the # sign, which browsers never send to a server. Your last entry is remembered on this device only, so the form is ready next time.