IQ Range and Scale by Age: Full Chart
The key to an IQ range and scale by age is simple: modern IQ scores are adjusted against people of the same age. A score of 100 is therefore the normed midpoint for a child, a young adult, and an older adult; it is not the number of questions answered correctly. The age-specific norm turns a raw result into a comparable standard score.
That distinction matters because raw cognitive performance and the reported IQ number do not follow the same path across life. Processing speed, vocabulary, memory, and reasoning can develop or change at different rates, while the test's reference point is recalculated for each age group. The chart below shows how to read the scale without mistaking an age norm for a prediction of ability.
What does the IQ scale mean at every age?
On the common deviation-IQ scale, the mean is 100 and the standard deviation is 15. The same score bands are used across age norms, so the percentile meaning is broadly stable even though the questions and expected raw performance change. APA describes this as a deviation IQ rather than the older mental-age divided by chronological-age formula.
| IQ score | Standard deviations from age mean | Approximate percentile | Plain-language reading |
|---|---|---|---|
| 70 | -2.00 | 2nd | Very low relative to the age norm |
| 85 | -1.00 | 16th | Lower edge of the broad average band |
| 90 | -0.67 | 25th | Around one quarter score lower |
| 100 | 0.00 | 50th | At the age-normed midpoint |
| 110 | +0.67 | 75th | Above roughly three quarters of peers |
| 115 | +1.00 | 84th | Upper edge of the broad average band |
| 130 | +2.00 | 98th | Uncommon high score |
These percentiles are mathematical approximations for a normally distributed scale with a standard deviation of 15. A real report may differ slightly because tests use their own norming sample, rounding rules, confidence intervals, and score ceilings.
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How are IQ scores adjusted for age?
First, the examiner records raw performance: correct answers, timing, and sometimes partial-credit rules. That raw score is then compared with the distribution for the examinee's exact age or a narrow age band in the test's norming sample. The conversion produces subtest scores, index scores, and sometimes a Full Scale IQ.
For example, a raw score that is typical for a 7-year-old would not be expected to be typical for a 17-year-old. Age norms prevent that raw difference from being misread as a direct intelligence difference. The resulting 100 means “near the middle of the relevant reference group,” not “the same number of items as everyone else.”
Age adjustment does not make two tests identical. A WISC, WAIS, Stanford-Binet, and a short online quiz can measure overlapping abilities while using different items, norms, administration rules, and reliability. Always read the test name and edition beside the score.
Which IQ test covers each age range?
There is no single test for every stage of life. The appropriate instrument depends on age, referral question, language, motor or communication needs, and local availability. Pearson's published age ranges illustrate the usual handoff points in the Wechsler family:
| Test | Published age range | Typical use |
|---|---|---|
| WPPSI-IV | 2 years 6 months–7 years 7 months | Preschool and early primary assessment |
| WISC-V | 6 years 0 months–16 years 11 months | Children and adolescents |
| WAIS-5 | 16 years 0 months–90 years 11 months | Older adolescents and adults |
The overlap around age 6–7 and age 16 is intentional. A qualified professional chooses the version that best fits the child's development and the reason for testing. At age 16, Pearson notes that WISC-V and WAIS-5 selection can depend on whether the concern is low scores, high ability, or an average-range evaluation. Do not choose a test solely because an internet chart lists it as “for adults” or “for children.”
Does the average IQ change with age?
The reported average stays near 100 within each age norm by design. That does not mean every cognitive ability is constant. In a cross-sectional comparison, younger and older groups may show different raw performance in processing speed or novel problem solving, while vocabulary and acquired knowledge can remain stable or improve longer. A normed IQ score answers a narrower question: how did this person's performance compare with same-age peers on this assessment?
This is also why a viral chart that assigns an “average IQ of 108 at age 16” is usually mixing raw scores, age-equivalent scores, and standard scores. Age-equivalent language can be useful for describing a particular skill, but it is not an IQ and should not be converted into one without the test manual.
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How should you read an IQ range by age?
Use this sequence when a report gives you a score:
- Check the instrument and edition. Confirm whether the result came from a standardized assessment or an informal quiz.
- Check the norm group. Look for the age range, language, country, and date of the norming sample.
- Read the confidence interval. A score such as 102 is an estimate; the report may give a range around it because measurement has error.
- Inspect the profile. Verbal comprehension, visual-spatial reasoning, fluid reasoning, working memory, and processing speed may not be equally strong.
- Match the interpretation to the purpose. A school placement, clinical evaluation, and personal curiosity require different levels of evidence.
An age-adjusted score is most useful when paired with the examiner's interpretation. NCBI guidance emphasizes that the validity and stability of a composite score depend on age, health, and the time since testing. A fresh, comprehensive assessment is more informative than comparing an old score with a newer online quiz that uses unknown norms.
Can you compare IQ scores from different ages?
You can compare standard scores cautiously when the tests use comparable norms and constructs, but you should not compare raw totals or age-equivalent labels directly. A 12-year-old's IQ of 115 and a 40-year-old's IQ of 115 both indicate performance around the 84th percentile of their respective norm groups; they do not mean the two people solved the same items or have identical abilities.
Scores also move within a person. Sleep, illness, anxiety, practice, motivation, sensory factors, and changes in the test edition can affect performance. Small changes may fall inside the confidence interval rather than represent a real change. For high-stakes decisions, ask the examiner whether the difference is statistically and clinically meaningful.
Q: Is the average IQ 100 at every age?
A: Approximately, within a properly normed test. The mean is set near 100 for each age group, so the number is a relative position rather than a raw ability total.
Q: Does an IQ of 100 mean a child and adult have the same ability?
A: No. It means each performed near the midpoint of their own age norm. The tasks, raw scores, development, and life experience can be very different.
Q: What IQ range is considered average?
A: About 85–115 on a scale with a mean of 100 and a standard deviation of 15. Labels vary by test, and a confidence interval should be considered before drawing conclusions.
Q: Which IQ test is used for a 16-year-old?
A: It depends on the referral question and professional judgment. WISC-V and WAIS-5 both cover age 16 in their published ranges, so the examiner chooses the instrument with the most appropriate floor, ceiling, norms, and clinical fit.
Q: Can I convert a raw score or age-equivalent score into IQ?
A: Not reliably without the test's official norms. Raw and age-equivalent scores are not interchangeable with deviation IQ, and online conversion charts can use the wrong edition or reference group.
References
- American Psychological Association: IQ
- Pearson Assessments: WPPSI-IV age range and scoring
- Pearson Assessments: WAIS-5 age range and updated norms
- NCBI Bookshelf: The Role of Intellectual Assessment
Last updated: July 18, 2026
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