✷ Free Stellium Calculator: Do You Have One?

Umbriel's free stellium calculator shows every cluster of planets in a single sign and in a single house in your birth chart, with exact degrees.

A stellium is a stack of planets bunched into one sign or one house, read as a concentration of emphasis: a lot of the chart's attention pointing at one place. That much is agreed. Almost nothing else about it is.

Some astrologers require three planets, some insist on four. Some count only the traditional seven; others include Uranus, Neptune, Pluto, the Ascendant, the Midheaven, Chiron or the nodes, which changes the answer for a great many charts. Some count by sign, some by house, and the two rarely agree. A group spread across a sign boundary can be a house stellium and not a sign one, and vice versa. A calculator that just announces "you have a stellium" has quietly picked one of these rulebooks without telling you.

So the useful question is not whether you have one but how tight the grouping is. Three planets spread across twenty-five degrees of a sign behave very differently from three sitting within four degrees of each other, where they are also conjunct and read as a single fused voice. Umbriel gives you the degrees and the conjunctions, which is the information the label is standing in for.

A stellium is three or more planets in one sign, and Umbriel finds it by reading each planet's sign from your birth chart and counting. The count uses the ten planets from the Sun to Pluto only; the nodes, Chiron, Lilith, asteroids and the angles are not counted. Any sign holding three or more of them is reported as a stellium, and a second such sign is reported as a second stellium. The sign of each planet comes from the same engine as the rest of the chart, so it is tropical unless you have chosen a sidereal zodiac, in which case the ayanamsa is subtracted from every longitude before the sign is read. Whether you have a stellium by sign does not depend on the birthplace, and it depends on the birth time only when a planet is near a sign boundary; the Moon is the body most likely to be, because it averages about 13 degrees a day. A grouping by house is different: each planet's house comes from the cusps of your chosen house system, which need an exact birth time and place, and without a birth time Umbriel gives no houses at all. The threshold of three is the rule this code applies, and the word has no formal definition. The accuracy page gives the Sun as under 1 arcsecond, the Moon as 0.27 arcminutes, Jupiter, Saturn, Uranus and Neptune as within 2.5 arcseconds, and Mercury, Venus and Mars as under 0.2 degrees, so a planet's sign is in doubt against the reference only when it sits that close to a boundary.