Question
What is a Full Scale IQ?
Short answer
Full Scale IQ (FSIQ) is the overall score on a clinical intelligence test such as the WAIS-5 or WISC-V. It combines a set of subtests, seven on both of those tests, into one number on a scale with a mean of 100 and a standard deviation of 15. Index scores break the same performance into separate abilities.
Want your own number? The test is 25 visual puzzles, about 12 minutes, no sign-up.
How FSIQ is built
Clinical batteries give many short subtests, each aimed at a narrower skill. A subset of them feeds the Full Scale IQ. On the WAIS-5 the FSIQ uses seven subtests, and Pearson says it can be obtained about 20 minutes faster than on the WAIS-IV (Pearson: WAIS-5). The WISC-V FSIQ is also based on seven subtests (Pearson: WISC-V).
Subtest scores and composite scores use different metrics. On the WISC-V, subtest scaled scores have a mean of 10 and a standard deviation of 3, while the primary index scores and the FSIQ use a mean of 100 and a standard deviation of 15. The FSIQ ranges from 40 to 160 (Pearson: WISC-V UK sample report).
Try one · Quantitative Reasoning
Which number comes next?
3, 8, 15, 24, 35, ?
Tap the option you think is right, or show the answer.
Show the answer
The next number is 48 (option 2).
How to solve it
- The gaps (5, 7, 9, 11) grow by 2 each time, which is the pattern of square numbers.
- Each number is a square number minus 1: 2 × 2 - 1, 3 × 3 - 1, 4 × 4 - 1, 5 × 5 - 1, 6 × 6 - 1.
- So the next number is 7 × 7 - 1 = 48.
That was 1 puzzle. The full test has 25.
FSIQ and the index scores
The WAIS-5 reports five primary indexes: Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory and Processing Speed (Pearson: WAIS-5 overview). The WISC-V uses the same five (Pearson: WISC-V). Ancillary scores add other summaries, such as a General Ability Index on the WAIS-5 (Pearson: WAIS-5 overview).
| Score | What it summarizes | Mean, SD |
|---|---|---|
| Full Scale IQ | Overall performance across the FSIQ subtests | 100, 15 |
| Primary index | One broad ability, such as working memory | 100, 15 |
| Subtest scaled score | A single subtest | 10, 3 |
When FSIQ tells less of the story
An overall score is most useful when a person's abilities are fairly even. If one index is far above or below the others, the single FSIQ hides that pattern, and the indexes are more informative read one by one. That is why a clinical report gives far more than one number.
FSIQ and online estimates
An online test can estimate overall reasoning ability, but it is not an FSIQ and cannot be used where one is required, such as for Mensa prior evidence, which needs a Wechsler test given in full (American Mensa: qualifying scores). For the tests themselves, see WAIS-5 and WISC-V; for score bands, see IQ classification.
Sources
- Pearson. Wechsler Adult Intelligence Scale, Fifth Edition (WAIS-5), product page. 2024. www.pearsonassessments.com/store/usassessments/en/Store/Professional-Assessments/Cognition-%26-Neuro/Wechsler-Adult-Intelligence-Scale-%7C-Fifth-Edition/p/P100071002.html
- Pearson. WAIS-5 overview brochure (C12396). 2025. www.pearsonassessments.com/content/dam/school/global/clinical/us/assets/wais-5/wais-5-overview-brochure.pdf
- Pearson. Wechsler Intelligence Scale for Children, Fifth Edition (WISC-V), product page. 2014. www.pearsonassessments.com/store/usassessments/en/Store/Professional-Assessments/Cognition-%26-Neuro/Wechsler-Intelligence-Scale-for-Children-%7C-Fifth-Edition/p/100000771.html
- Pearson Clinical UK. WISC-V UK sample interpretive report (Q-global). 2016. www.pearsonclinical.co.uk/content/dam/school/global/clinical/uk-clinical/files/wisc5-sample-interpretive-report.pdf
- American Mensa. Qualifying test scores. www.us.mensa.org/join/testscores/qualifying-test-scores/
- IQ classification. Wikipedia. en.wikipedia.org/wiki/IQ_classification