The answer depends on what you mean by “personalities.” If you’re asking about personality types, the most widely used system defines 16. If you’re asking how many separate identities a person with dissociative identity disorder (DID) can have, the average is about 10, though the range spans from 2 to over 100. And if you’re asking how many basic personality dimensions exist in every person, most psychologists settle on five or six core traits that combine in endless variations.
Each of these frameworks answers a different version of your question, so let’s break them down.
Personality Types: 9, 16, or More
Several popular systems attempt to sort people into distinct personality types. The most well-known is the Myers-Briggs Type Indicator (MBTI), which defines 16 personality types. It works by combining four either/or preferences: introversion vs. extraversion, sensing vs. intuition, thinking vs. feeling, and judging vs. perceiving. Every possible combination of those four pairs produces 16 types, each with its own shorthand label like INFP or ESTJ.
The Enneagram is another popular model, and it uses nine interconnected personality types rather than 16. Each type represents a core motivation or worldview, from “The Perfectionist” to “The Peacemaker,” with variations called “wings” that blend traits from neighboring types.
These systems are widely used in workplaces, relationships, and self-help contexts, but they’re not considered rigorous science. Most academic psychologists prefer trait-based models over type-based ones, because putting people into boxes tends to oversimplify how personality actually works.
The Big Five Personality Traits
In research psychology, the dominant model doesn’t sort people into types at all. Instead, it measures where you fall on five broad trait dimensions, often called the Big Five or remembered by the acronym OCEAN:
- Openness to experience: your level of curiosity, imagination, and willingness to try new things
- Conscientiousness: how organized, disciplined, and goal-oriented you are
- Extraversion: your sociability, talkativeness, and comfort drawing energy from other people
- Agreeableness: how cooperative, kind, and trusting you tend to be
- Neuroticism: your tendency toward sadness, anxiety, and emotional instability
Everyone has some level of all five traits. You’re not “an extravert” or “a neurotic” in this model. You simply score higher or lower on each dimension, creating a unique profile. Because each trait exists on a spectrum, the number of possible personality combinations is essentially infinite.
A newer model called HEXACO expands the Big Five to six dimensions by adding Honesty-Humility, which captures sincerity, fairness, modesty, and lack of greed. This sixth factor emerged when researchers studied personality structure across diverse languages and consistently found that five factors weren’t quite enough. HEXACO also reshuffles some trait content: its version of Emotionality and Agreeableness are rotated differently from their Big Five equivalents, and its Openness dimension excludes raw intellect or mental ability.
Multiple Personalities in DID
If your question is about one person having multiple personalities, you’re asking about dissociative identity disorder. DID involves two or more distinct identities, often called “alters,” that take turns controlling a person’s behavior, memory, and thinking. The shifts happen involuntarily and cause real distress. Someone experiencing a switch might suddenly change their food preferences, clothing choices, or even feel like they’re in a different body, such as feeling like a small child or like someone of a different gender.
The number of alters varies enormously. A person with DID may have as few as 2 or as many as 100. The average is about 10. Not all of these are fully developed identities, though. Clinicians distinguish between alters and fragments. A fragment is a less developed identity that may exist to carry out a single function, hold one specific memory, or represent one emotion. Fragments typically haven’t been exposed to enough varied experiences to develop a full sense of self. They can become more elaborate over time if circumstances require it.
DID develops as a response to severe, repeated trauma, usually in early childhood. The separate identities form as a way for the mind to compartmentalize experiences that are too overwhelming to process as a single, unified self. The diagnostic criteria from the American Psychiatric Association require the presence of at least two distinct identity states, along with gaps in memory that go beyond ordinary forgetting.
Why the Answer Isn’t One Number
Personality itself is a complex, dynamic integration of traits, values, drives, emotional patterns, and life experiences. Psychologists broadly agree that personality helps determine behavior, but they disagree on how best to carve it up. Type systems like the MBTI give you a memorable label. Trait models like the Big Five give you a nuanced profile. And in DID, the very concept of “a personality” fractures in ways that don’t map onto either framework.
So if you’re looking for a single number: the Big Five gives you 5 core dimensions, the MBTI gives you 16 types, the Enneagram gives you 9, and someone with DID averages around 10 distinct identities. Which number matters most depends on the question you’re really asking.