The Five-Factor Model and the IPIP-NEO-120
When a personality profile claims to be built on science, the honest question is which science, and how well it holds up. This note covers the framework behind a credible work style profile. It covers the Five-Factor Model and the public-domain item set that measures it. It also covers where the comparison norms come from, and the real limits of what a self-report instrument can and cannot tell you.
How this note is governed
Applies to Employers and individuals using the IPIP-NEO-120 for development. A public-domain instrument, not a hiring test and not a clinical measure.
Short answer
5 domains, 30 facets. The Five-Factor Model describes five broad domains and thirty facets beneath them. The IPIP-NEO-120 is a 120-item public-domain measure of them, normed on more than 600,000 respondents. It is a development tool, not a hiring test.
Published Last verified
Johnson's 2014 development paper and the open normative dataset were rechecked. The reference sample of more than 600,000 respondents was unchanged.
- 600k+
- respondents make up the public-domain reference sample behind the IPIP-NEO-120 percentiles.
- 5
- broad domains, with thirty facets beneath them, are what the Big Five and the IPIP-NEO-120 measure.
Five dimensions that describe how people work
Personality research spent most of the twentieth century arguing over how many traits matter. By the early 1990s the field had largely converged. Researchers analyzed the words people use to describe each other. They also analyzed the way answers to thousands of questionnaire items cluster together. They kept arriving at the same five broad dimensions. Lewis Goldberg, who coined the term, called them the Big Five. The same structure, developed in parallel by Costa and McCrae as the Five-Factor Model, underlies the major commercial personality tools used in leadership development today.
The five are not a typology that sorts people into boxes. Each is a spectrum, and almost everyone lands somewhere in the middle of most of them. No end of any scale is better than the other. Each end carries its own strengths and its own costs. What the model gives you is a shared, evidence-based vocabulary for tendencies that show up at work every day.
A personalized workbook generated from your own profile. It carries a development chapter for each domain, targeted exercises for the facets where you score furthest from typical, and a 90-day plan.
The IPIP-NEO-120, and why public domain matters
A framework needs an instrument to make it usable, and the questions you answer have to be sound. The IPIP-NEO-120 draws its items from the International Personality Item Pool. That is a public, peer-reviewed collection of personality items used in hundreds of published studies. Dr. John A. Johnson assembled and validated the 120-item version, which measures all five domains plus six facets within each, for thirty facet scales in total. His development paper was published in the Journal of Research in Personality in 2014.
Public domain is not a detail. It is the credibility argument. The items are openly licensed and free for any use, including commercial, with no permission or fee required. That means anyone can read exactly what is being asked, how it is scored, and how it performs. The alternative is trusting a vendor that the contents of a proprietary, sealed instrument are valid. The science is auditable. A profile built on the IPIP-NEO-120 stands on the same five domains that sit underneath the better-known paid tools, with its methods in the open.
What a percentile here actually compares you to
A raw score on a personality scale means little on its own. To turn it into something readable, the score is compared against a reference sample to produce a percentile. A 70 means you scored higher than roughly seven in ten people in that sample. The IPIP-NEO-120 percentiles used here are referenced to the US subset of Johnson’s public-domain dataset. That is 243,171 complete responses from adults aged 18 to 75 who completed the inventory online.
One honest point about that sample, which a credible profile should state plainly rather than gloss over. These are people who chose to take a personality inventory online, not a representative cross-section of the whole population. They skew higher on Agreeableness and Conscientiousness than the general public would. That is why an average-looking raw score on those two traits can still land in a middle or even lower percentile band. The right way to read your result is as where you land among other people who took the same inventory. That is the fair comparison for self-understanding. It is not a ranking against every adult alive. Naming that limit is part of using the instrument honestly.
Development, not selection or diagnosis
The most important thing to understand about a Big Five profile is what it is not for. The research divides personality assessment into two purposes that carry very different burdens. Tools optimized for selection and hiring decisions live under heavy validation and legal requirements. Using them to choose who gets a job has consequences and is regulated accordingly. Tools for development and self-insight sit in a different, safer category: they help a person understand how they tend to operate and where to grow.
A work style profile built on the IPIP-NEO-120 belongs firmly in the second category. It is a mirror for self-understanding, coaching, and development conversations, not a hiring test, a promotion gate, or a clinical diagnosis. Personality describes how you tend to operate. It does not set a ceiling on what you can do. It should never be the thing that decides whether someone is hired or advanced. A profile that respects that line is being honest about its own science. One that blurs it, by hinting it can predict who to hire, is overclaiming.
Six red flags to check before you fire someone
Free, and written to the same standard
A five minute screen to run before you act, sent to your inbox as a print-ready PDF. Every figure in it traces to a reference note like this one.
Where these figures come from
6 citations checked, newest check 29 June 2026
- Johnson, J. A. (2014). Measuring thirty facets of the Five-Factor Model with a 120-item public domain inventory: Development of the IPIP-NEO-120. Journal of Research in Personality, 51, 78-89. The development and validation paper for the 120-item instrument, including its facet structure and the internet samples it was built on. doi.org doi.org
- International Personality Item Pool (ipip.ori.org). The public-domain source of the items, maintained as a scientific resource, openly licensed and free for any use including commercial. ipip.ori.org ipip.ori.org
- Johnson, J. A. IPIP-NEO-120 normative data repository (Open Science Framework). The public-domain dataset of more than 600,000 responses. The reference means, standard deviations, and percentiles used here come from its US subset of 243,171 complete responses aged 18 to 75. That includes the documentation that the sample is self-selected online respondents. osf.io osf.io
- Goldberg, L. R. (1993). The structure of phenotypic personality traits. American Psychologist, 48(1), 26-34. A foundational statement of the Big Five structure and the convergence of decades of trait research onto five dimensions. doi.org doi.org
- Barrick, M. R., and Mount, M. K. (1991). The Big Five personality dimensions and job performance: A meta-analysis. Personnel Psychology, 44(1), 1-26. The widely cited meta-analysis establishing Conscientiousness as the most consistent personality predictor of job performance across occupations. doi.org doi.org
- Soto, C. J., and John, O. P. (2017). The next Big Five Inventory (BFI-2). Journal of Personality and Social Psychology, 113(1), 117-143. A modern treatment of the five-domain, multiple-facet structure that the IPIP-NEO-120 also follows. doi.org doi.org
Common questions
Is the Big Five scientifically valid?
The Five-Factor Model is the most validated and widely accepted framework in personality science. Decades of research, across languages and cultures, converge on the same five broad domains. The same structure underlies the major commercial personality tools used in leadership development. It is the mainstream scientific consensus, not a single proprietary theory.
What is the IPIP-NEO-120?
It is a 120-item public-domain measure of the Five-Factor Model, developed and validated by Dr. John A. Johnson and published in 2014. It scores all five domains plus thirty facets and draws its items from the peer-reviewed International Personality Item Pool. It is free for anyone to use, read, and audit.
What does the percentile compare me to?
To the US reference sample of Johnson’s public-domain dataset: 243,171 adults who completed the IPIP-NEO-120 online. That sample is self-selected rather than nationally representative. It skews higher on Agreeableness and Conscientiousness than the general public. Read your percentile as where you land among other test-takers rather than against every adult.
Can I use a personality profile to make hiring decisions?
A development-focused Big Five profile is built for self-understanding and growth, not for selection. Hiring use carries validation and legal requirements that a development instrument is not designed for. Personality does not set a ceiling on what someone can do. Use it to develop people, not to decide who gets a job.
Put it to work
The free assessment itself: 120 questions, about 12 minutes, scored on the IPIP-NEO-120 with your five domains and thirty facets as percentiles. No sign-up to see your result.
FreeA personalized workbook generated from your own profile. It carries a development chapter for each domain, targeted exercises for the facets where you score furthest from typical, and a 90-day plan.
$39The manager-focused read. It covers how your five domains shape the way you lead, give feedback, delegate, and handle pressure. It carries the watch-outs your pattern tends to bring and scripts to manage them.
$69A profile is a starting point, not a plan. Work through the Work Style Profile, then read it with a senior HR practitioner in the $99 Results Debrief to translate your domains and facets into where to focus first.
$99
This note is general information about employment practice rather than legal advice for your situation. Check the review date and the jurisdictions above, follow the source link, and confirm the rule before you act on it.