Chart pattern
Stellium Calculator
A stellium is a pile-up: three or more planets crowded into the same sign, or into the same house. This tool counts yours, names the members, and tells you how common that result is. On the three-planet rule it turns out to be common, and the page says so rather than selling you a rarity.
What a stellium is, and what it isn't
A stellium is simply a count: several planets in the same sign, or the same house. Tradition reads one as a part of the chart that carries more than its share of the weight, an area of life that keeps getting written about. What it is not is a measured quantity. There is nothing in the ephemeris called a stellium; there are planetary longitudes, and a habit of noticing when several land together. Because it is a habit rather than a measurement, the counting rule is a choice, and different astrologers choose differently, which is why this page prints the rule it used instead of handing you a verdict.
The rule this page counts by
A few choices decide every stellium answer. Ours are these, stated so you can disagree with a specific one.
Ten planets, no points
Sun through Pluto count. Chiron, Lilith, the lunar nodes, the Part of Fortune, the Vertex and the angles do not. Points are not planets, and letting them in would manufacture clusters for almost everyone.
Three or more
Three is the common threshold, and it is the one used here. A stricter school asks for four, and on our sample that changes the answer for a lot of people: three-plus in one sign covers about seven charts in ten, four-plus about one in five. Your count is printed next to every group, so you can apply either rule yourself.
By sign and by house, not by orb
Membership is decided by which sign or which house a planet falls in. A third school wants the planets tightly conjunct within a set orb, which is a different instrument answering a different question: two planets at the opposite ends of the same sign are twenty-nine degrees apart and still count here.
Houses need the hour
House clusters use Placidus houses, so they require a birth time. Without one they are withheld rather than computed at noon and presented as fact. The sign clusters mostly do not depend on the hour; the exceptions are chiefly the Moon (it moves about thirteen degrees a day) and, now and then, a faster planet caught near a sign's edge, flagged when it is the body holding a group together.
Tropical signs, Placidus houses
The signs here are tropical, tied to the equinox, the frame used across most of the Western world, not sidereal. On a page entirely about which sign a planet sits in, that is the choice that moves the most charts, so it is named rather than assumed. Houses, where a birth time gives them, are Placidus.
How common is a stellium, really
Astrology writing treats a stellium as remarkable. Counted honestly, the three-planet version is not. We measured it on 6,000 randomly generated births between 1940 and 2009, at ten cities and random hours:
- Three or more planets in one sign
- 69 out of 100 charts
- Three or more in one house
- 72 out of 100 charts
- At least one cluster, sign or house
- 83 out of 100 charts
- Four or more in one sign
- 21 out of 100 charts
- No cluster at all
- 17 out of 100 charts
These rows overlap rather than divide a whole. A chart can hold both a sign cluster and a house one, and four-or-more sits inside three-or-more; only the last two, at least one cluster and none, are opposites that add up to 100.
Why it happens so often
Three things stack up, and only one of them is astronomy. First, arithmetic: drop ten planets into twelve signs and close to half the time three of them land together before any sky is involved at all, just from the counting. Second, the inner planets are tethered: Mercury and Venus never wander far from the Sun as seen from here, so across the whole range this tool covers Mercury stays within about 28 degrees of it and Venus within about 48. That puts the Sun, Mercury and Venus in one sign on roughly one day in eight. Third, the slow planets sit in one sign for years at a time, so any two of them a birth happens to catch together pick up a third easily. Having a stellium is ordinary; which sign or house it falls in is the part that is yours.
Why the house number runs higher
House clusters come out a touch more common than sign ones, and more so the farther from the equator you were born. Placidus houses, the system here, are unequal in size: near the poles a single house can span far more than a whole sign, so three planets in one house can sit further apart than three in one sign. A whole-sign astrologer counts houses another way and will sometimes reach a different verdict for the same chart, which is one more reason the rule is printed rather than assumed.
If you count to four
The stricter school asks for four planets before it calls a pile-up a stellium, and there the rarity is real: about one chart in five has four or more in a single sign, roughly one in three once you let a house hold them too. Every group above prints its member count, so you can hold either line without recomputing anything.
If you don't know your birth time
You still get an answer. Sign clusters come from the date, and nine of the ten planets barely move in a day. The Moon is the exception, covering about thirteen degrees, so it can change sign between midnight and midnight; when a group only reaches three because of the Moon, the result says so. House clusters are the part that genuinely needs the hour, and they are left out rather than filled in from a noon guess.
Questions people ask
Is having a stellium rare?
On the three-planet rule, no. In our sample of 6,000 births, 69 in 100 charts had three or more planets in one sign, and 83 in 100 had a cluster in a sign or a house. Rarity starts higher up: four or more in one sign appeared in about 21 charts in 100. If a page tells you a three-planet stellium makes you unusual, it has not counted.
Do I need my birth time?
For sign clusters, almost never: nine of the ten planets barely move in a day, so the date fixes their signs. The exception is a body sitting right on a sign's edge at noon, most often the Moon, and the result flags that one. For house clusters, yes: houses are built from the hour and the birthplace, so without a time this tool shows the sign half and says the house half is missing, rather than computing it at noon and presenting it as your chart.
Is it three planets or four?
Both rules are in use. Three is the more common one and the one this page counts by; four is the stricter school, and on our sample it separates about one chart in five from the rest. Every group here prints its member count, so you can hold whichever line you prefer without recomputing anything.
My Sun, Mercury and Venus are together. Does that count?
Under the three-planet rule it counts, and it is the single most common way a stellium forms, though it is far from the only one. Mercury and Venus orbit closer to the Sun than we do, so from here they stay near it: within about 28 and 48 degrees of longitude respectively. That is why this particular trio shows up so often, and why some astrologers ask for a fourth planet before calling it a signature.
Why doesn't my Chiron or my North Node count here?
Because this page counts the ten planets only. Chiron is a small body between Saturn and Uranus, and the nodes are a pair of calculated points rather than objects. Both are read by plenty of astrologers, and both would add clusters to a great many charts if we let them in. The rule is stated so that our answer and another site's can be compared instead of just contradicting each other.
Can I have more than one stellium?
Yes. Astrologers read a stellium as a focal point, an area of the chart concentrated enough to be hard to ignore, so two of them means two such areas pulling at your life, and the reading looks at how the two play against each other. One caution in the counting: the same planets crowded into a sign usually crowd into a house too, and that is one pile counted two ways, not two stelliums, so we mark it as one. Genuinely separate clusters, different planets gathering in different signs or houses, are less common, and this tool lists every one it finds with its members, so you can see exactly what you have.