IQ Scale by Age: Which IQ Test Fits Each Age and What the Scores Mean

The IQ scale is the same at every age, but the test is not. A score of 100 means average for your own age group whether you are 6 or 66, because every modern IQ test compares you with people of your age. What changes with age is the instrument: the WPPSI-IV covers 2 years 6 months to 7 years 7 months, the WISC-V covers 6 to 16, the WAIS-IV and WAIS-5 cover 16 to 90, and the Stanford-Binet 5 spans 2 to 85 and over. The table below shows which test fits which age.

Understanding how IQ scores relate to different age groups can help you interpret test results more meaningfully. IQ, or intelligence quotient, is a standardized measure of cognitive abilities such as reasoning, memory, and problem-solving. While IQ is generally stable in adulthood, age-related trends and life experiences can influence performance on different types of tasks.

Which IQ test is used at each age?

IQ tests are built for an age range, because the questions, the norm tables and the examiner’s procedure all change with age. The table shows which common test covers which ages, using the ranges given in our test guides.

Group tests such as the OLSAT report on a different scale, so convert before comparing: the IQ score converter does it in one step. For which age gives the most dependable result, read what age is most accurate to take an IQ test and IQ testing for children.

What is the average IQ at each age?

Exactly 100 at every age. The average IQ of a 5-year-old, a 10-year-old, a 16-year-old, a 30-year-old and a 70-year-old is the same, because the norm tables are built age band by age band and a score compares you only with your own age group. What changes with age is raw performance, the number of questions answered correctly. Our core page IQ and age explains why every age group averages 100, and why an old IQ score does not match a new one covers what happens when the norms themselves age.

How was a child's IQ calculated before age norms?

The first IQ was a ratio: mental age divided by chronological age, multiplied by 100. A mental age is the age of the average child who earns the same raw score, so a child aged 8 who performs like the average 10-year-old has a mental age of 10 and a ratio IQ of 10 / 8 x 100 = 125.

The formula broke down for adults, because mental age levels off while chronological age keeps rising, and the spread of ratio IQs differs from one age to another, so scores could not be compared across ages. Modern tests replaced it with the deviation IQ, which compares a person with others of the same age on a scale with a fixed mean and standard deviation. See deviation IQ vs ratio IQ and IQ and mental age.

The IQ: A definition and explanation

A thorough familiarity with the IQ scale is required prior to exploring the subject of IQ score changes over time. A person’s intelligence quotient (IQ) is a measure of their cognitive abilities, which include their memory, reasoning, problem-solving, and language skills. The average score on an IQ test is 100 and the standard deviation is 15. Most people score between 85 and 115; a score below 70 is one criterion for intellectual disability, and a score above 130 is in the top 2%.

In order to gauge a person’s intelligence, an IQ test will usually comprise a battery of questions or activities. Standardisation and understanding the typical behaviour of a certain age group are two goals of administering the exams to large samples of the population. To determine an individual’s IQ, test scores are compared to predetermined standards.

Things that influence IQs

Numerous factors can influence an individual’s IQ. Genetic factors have a significant impact on cognitive ability, according to the notion that intelligence is partially inherited. At the same time, environmental influences may influence IQ scores. A person’s intelligence quotient (IQ) is affected by a variety of elements that impact their brain development. These determinants include things like a person’s social status, cultural background, dietary habits, and access to education.

In the first years of life, a child’s cognitive growth is shaped by the home environment, parental involvement and the quality of schooling. Later, education, health and the kind of work a person does are all linked to test performance, and a score can also move a little from one sitting to the next through ordinary measurement error.

Does age have any bearing on intelligence?

Age changes what people can do, but not the IQ scale. Because each score compares you with people of your own age group, the average is 100 at every age: a 10-year-old and a 70-year-old can both score exactly 100 while answering very different numbers of questions correctly. The change lives in raw performance. Processing speed peaks in the twenties, while vocabulary and knowledge keep climbing into the sixties (at what age intelligence peaks).

Children are where age matters most. Their raw performance rises quickly from year to year, which is why they are tested with age-specific instruments and norm tables, and why a child’s score is less stable than an adult’s (see below). Our page on IQ and age explains why a child’s IQ moves more than an adult’s.

In later life the picture is mixed. Speed-dependent tasks decline from early adulthood while knowledge-based ones hold up much longer, so an older adult’s report often shows a wide gap between index scores: strong on vocabulary and comprehension, weaker on timed and novel material (full-scale IQ vs index scores). The total IQ stays centred on 100 because it is recalculated against people of the same age.

Across generations, average scores on a fixed test rose for most of the twentieth century, a trend named the Flynn effect after the researcher James Flynn, who documented it in the 1980s. Reasons given include better nutrition, more years of schooling and a more cognitively demanding society.

How stable is IQ from childhood into adulthood?

Fairly stable in adulthood, much less so in childhood. A 2024 meta-analysis of 205 longitudinal studies (87,408 participants) found a mean rank-order stability of .76 for people aged 20 retested five years later. Stability was low in preschool children, rose rapidly through childhood and stayed consistently high from late adolescence to late adulthood. The authors estimate that stability high enough for individual-level diagnostic decisions (a test-retest correlation of .80) can only be expected over the age of 7 and for short intervals in children (Breit and colleagues, 2024).

Over a lifetime the link is weaker but real. In the Lothian Birth Cohort of 1921, the same intelligence test (the Moray House Test) taken at age 11 and again at age 90 correlated .54, or .67 once corrected for range restriction (Deary, Pattie and Starr, 2013; 106 people). For infants, early measures predict later IQ only modestly: our baby IQ test guide reports a weighted correlation of about .36 for looking-time tasks in the first year. A modest correlation means high early scores tend to come down and low ones tend to go up, an effect explained on regression to the mean; the study of 11,119 children puts numbers on it.

The origins of IQ tests and the Flynn effect

The Flynn effect matters for age comparisons because a score is only meaningful against norms collected from people of the same age and era. As norms age, scores drift upward, which is why tests are revised and re-normed every decade or two and why an old score cannot be compared directly with a new one (why your old IQ score does not match a new one).

As the Flynn effect shows, an increasing proportion of people from all walks of life and economic backgrounds have experienced an increase in their IQ during the past century. Growth in cognitive capacity, including the capacity to think critically and solve problems, is due more to external factors than to intrinsic traits. The increasing complexity of modern life, along with improvements in nutrition, educational opportunities, and technology, is largely responsible for the general rising trend in IQ assessments.

Gains of this kind have been recorded in many countries, and they have been too fast to be genetic. In some countries the rise has since slowed, which is another reason norms expire (why IQ norms expire).

The benefits and drawbacks of intelligence testing for various age groups

Despite their widespread use, IQ tests have limitations that become more apparent when comparing results from different age groups. As a measure of cognitive ability, intelligence quotient (IQ) exams look at things like processing speed, working memory capacity, and language understanding. However, it’s conceivable that these tests don’t account for all potential cognitive capacities or give erroneous IQ scores for different age groups.

Impatience with test forms, limited attention span, and immaturity in linguistic abilities are some of the reasons why children’s IQ scores may be misleading. Even more concerning is the idea that intelligence tests, which focus on aspects of intelligence that can decline with age, fail to account for the unique characteristics and abilities of the elderly.

This is an important consideration when comparing IQ testing for individuals of various ages. Like any thorough evaluation tool, IQ testing should account for factors like cultural influences, life experiences, and educational level.

Achieving a higher IQ regardless of age

Intelligence is a trait that can be honed at any age, so it’s vital to keep that in mind even though IQs could vary from generation to generation. There is a wide variety of approaches that can raise an individual’s intelligence and cognitive capacity:

Young children’s cognitive development is greatly enhanced when they are provided with a stimulating and caring environment during their formative years. Improving one’s cognitive capacities and establishing the groundwork for future intellectual growth can be achieved through reading, solving puzzles, and playing educational games.

Academics and other kinds of intellectual stimulation should be front and centre throughout adolescence. Engaging in cognitively taxing activities, thinking critically, and solving problems are all ways to promote cognitive development and keep or raise IQ levels.

A lifelong commitment to learning will pay dividends in the form of a healthy, bright brain as you age. It is suggested that regular exercise, staying educated, and participating in mentally difficult activities might help preserve or even increase cognitive function and IQ.

As we get older, it is more important than ever to engage in activities that promote brain health and cognitive vitality. Exercise, social contact, and cognitive training can preserve or even enhance cognitive capacities, especially the IQ-evaluable aspects of intelligence.

Keeping one’s mind active requires a dedication to lifelong learning, since intelligence tests show that IQs decline with age. Brain health and potential IQ enhancement can be achieved by consistent practice of mentally taxing activities and an insatiable appetite for knowledge.

The advantages of continuing one’s education throughout life go far beyond how well one does on IQ testing. In addition to enhancing brain health, memory, and cognitive flexibility, it protects against cognitive decline and neurodegenerative diseases. Individual development, enhanced health, and a broader range of knowledge and skills are further advantages of continuing one’s education throughout life.

Adopting a growth mindset, which promotes an endless quest for knowledge, improves one’s adaptability to a continuously changing world and fosters one’s innate curiosity. When individuals proactively pursue new information, mentally challenge themselves, and embrace intellectual curiosity, they can achieve rich, intellectually robust lives.

The bottom line on IQ and age

IQ is a position within an age group, not a measure of raw ability, so it does not rise and fall the way performance does. It is fairly stable from adolescence to late adulthood, less stable in childhood, and it can move a few points between tests through measurement error alone (an IQ score is a range, not a number).

The practical rules are short: use a test built for the age (the table above), read the score against the scale it was printed on, and treat a single number as roughly 5 points either side. For the numbers behind each band, see IQ ranges, IQ classification and IQ test range.

Sources

• Breit, M., Scherrer, V., Tucker-Drob, E.M. and Preckel, F. (2024): The stability of cognitive abilities: a meta-analytic review of longitudinal studies, Psychological Bulletin, 150(4), 399-439.
• Deary, I.J., Pattie, A. and Starr, J.M. (2013): The stability of intelligence from age 11 to age 90 years: the Lothian Birth Cohort of 1921, Psychological Science, 24(12), 2361-2368.
• Test age ranges, norm-sample sizes and scales are those given in our own guides linked above.

If you’d like to better understand your own cognitive strengths and how your score fits into broader demographics, you can take an online IQ test on our homepage.