What Does IQ Stand For?
Quick Answer
IQ stands for Intelligence Quotient. The term was coined by psychologist William Stern in 1912, when scores were calculated as a quotient: mental age divided by chronological age, multiplied by 100. Modern tests no longer use that division, but the name stuck.
Why Is It Called a 'Quotient'?
The original IQ formula really was a quotient — a division problem. Early tests like the Binet-Simon scale estimated a child's 'mental age' from their answers, then divided it by their actual age and multiplied by 100. A 10-year-old performing like a typical 12-year-old scored 120 (12 ÷ 10 × 100).
That formula broke down for adults — mental age plateaus, so an adult's ratio IQ would nonsensically decline every birthday. In 1939, David Wechsler replaced it with the 'deviation IQ' still used today: your score reflects how far you sit from the average of your age group on a bell curve with a mean of 100 and a standard deviation of 15.
What IQ Means Today
On modern tests like the WAIS-IV and Stanford-Binet 5, IQ is a statistical ranking, not a measurement of a physical quantity. A score of 100 means you performed exactly at the median for your age group. A score of 115 places you one standard deviation above — roughly the 84th percentile.
So while 'Intelligence Quotient' is technically a historical misnomer, the underlying idea survives: IQ expresses your measured reasoning performance relative to everyone else your age.
Frequently Asked Questions
Who invented the term IQ?
German psychologist William Stern coined 'Intelligenzquotient' in 1912 to describe the ratio of mental age to chronological age. Lewis Terman popularized the term when he published the Stanford-Binet test in 1916.
Is IQ still calculated as a quotient?
No. Modern tests use 'deviation IQ' — your performance compared to a normed sample of your age group, placed on a bell curve with mean 100 and standard deviation 15. No division is involved.
What does a 100 IQ mean?
A score of 100 is by definition the exact average for your age group. Roughly two-thirds of people score between 85 and 115.
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MyIQScores Editorial Team
Researchers in cognitive psychology, psychometrics & educational science
Last updated
May 10, 2026
All content on MyIQScores is reviewed for scientific accuracy against peer-reviewed research in cognitive psychology and psychometrics. Our editorial team cross-references each article with published literature before publication and updates pages whenever new research warrants a revision.