In brief: A stellium is a concentration of planets, but there is no single counting rule. Three or more in one sign or house is a broad usage; some readers require a close conjunction or at least four bodies.
How many planets count?
Different definitions test a shared sign, a shared house, or closeness by degree. Check the rule used before comparing two readings.
| Grouping | Minimum | What to check |
|---|---|---|
| Same sign or house | 3+ | A shared sign or house; degree spread may vary |
| Close conjunction | 3+ | A tight cluster by zodiac degree |
| Stricter grouping | 4+ | Four bodies in one sign or house |
How many planets make a stellium?
A broad modern answer is three or more planets in the same sign or house. Other astrologers reserve the word for planets closely conjunct by degree, and some require four or more bodies. These rules can give different answers for the same chart. Before asking whether you have a stellium, decide what you are counting: planets, the Sun and Moon, or additional chart points. State the rule rather than treating every online count as interchangeable.
Sign, house, and degree are separate tests
A sign stellium groups bodies in one zodiac sign; a house stellium groups them in one chart house. Neither guarantees that all the bodies sit close together by degree. A conjunction-focused definition asks how near the bodies are along the zodiac, even when a sign boundary runs through the group. Look at the actual longitudes and house cusps before naming the pattern. The examples below use invented positions to show how the answers change, not a published birth chart.
Example 1: three planets in Leo
In a hypothetical Aries-rising Whole Sign chart, the Sun at 4° Leo, Mercury at 8° Leo, and Venus at 11° Leo all fall in the fifth house. They span 7° from first to last. This is a three-body Leo sign and house cluster, and a close degree group under many conjunction-based readings. It does not satisfy a four-body threshold.
Example 2: one house, two signs
Imagine a quadrant chart whose seventh house extends from 24° Virgo to 26° Libra. The Moon at 28° Virgo, Venus at 1° Libra, and Mars at 4° Libra all occupy that house and span 6° across the sign boundary. A three-body house or close-conjunction reading can count the group; a single-sign reading cannot. The house claim depends on the stated birth time and house system.
Non-example: two together, one elsewhere
In a hypothetical Aries-rising Whole Sign chart, the Sun at 4° Leo and Mercury at 8° Leo occupy the fifth house, while Mars at 14° Virgo occupies the sixth. This is not a three-body cluster by sign, house, or close degree. Calling it a stellium merely because all three planets appear in the same part of a chart wheel would hide the actual positions.
Why birth time and house system matter
You can often check a sign cluster from a dated chart without a precise birth hour, although the Moon may cross a sign boundary during the day. A house cluster depends more heavily on birth time, birthplace, and the house system. If the recorded time is approximate, a planet near a cusp may move to another house when the chart is recalculated. Keep the sign grouping and the house grouping distinct; one can remain clear while the other is uncertain.
How to read a concentration
A cluster can direct attention to the sign or house it occupies, but it does not turn several planets into one personality trait. Each body keeps its own position, role, and aspects. Three slow outer planets close together may describe many people born in the same period; faster planets and angles can make a particular chart more specific. Compare the cluster with the rest of the chart, including planets elsewhere and aspects that complicate a simple story. The definition tells you what you are looking at; it does not predict an outcome.