Mental Age Calculator

No. Reasoning ability levels off in early adulthood, but your actual age keeps rising, so the ratio of mental age to actual age would fall every year for no real reason. A 60-year-old with an IQ of 74 would get a mental age of 44 years 5 months from the plain formula, which no psychologist would say describes how they think.

Early test makers handled this by capping the age used in the formula at about 16. On that convention an adult with an IQ of 74 gets a mental age of 11 years 10 months. That is a historical convention, not a finding about adults, and modern tests do not report it. An adult IQ says where you stand among people your own age, and nothing more.

If you are looking at an adult's score, the IQ test for adults page explains how scores are spread, and the average IQ by age calculator gives a percentile for any age.

Mental age = (IQ ÷ 100) × actual age. To go the other way: IQ = (mental age ÷ actual age) × 100.

For a precise answer, use months. A child aged 8 years 6 months is 102 months old. With an IQ of 120, the mental age is (120 ÷ 100) × 102 = 122 months, which is 10 years 2 months.

An IQ above 100 gives a mental age above your real age. An IQ below 100 gives a lower one. At exactly 100, the two match. For a way to read an IQ against other people your age instead, use the IQ percentile chart.

Alfred Binet and Théodore Simon introduced mental age in 1905 as part of the first practical intelligence test. A child's mental age was the age group whose test items they could complete.

In 1912, William Stern proposed the intelligence quotient as mental age divided by chronological age, times 100. A 10-year-old with a mental age of 12 had an IQ of (12 ÷ 10) × 100 = 120.

David Wechsler replaced this ratio IQ with the deviation IQ in 1939. It compares your performance with the spread of scores for your age group, with an average of 100 and a standard deviation of 15. Every modern test uses it. To see where a modern score sits, try average IQ by age or the IQ bell curve.

The ratio approach fails for adults because reasoning ability levels off in early adulthood, so the ratio of mental age to real age stops meaning much as you get older. It also has a second flaw: the spread of ratio IQs is not the same at every age, so the same ratio IQ does not mean the same rarity at 6 and at 12. The deviation IQ fixes both by comparing each person only with their own age group.

For the modern scale by age, see average IQ for children by age and the IQ test for kids and children parent guide.