What is the normal IQ range for humans?

The concept of “intelligence” has largely been replaced by the notion of IQ (intelligence quotient). In many cases, our IQ score closely correlates with how intelligent we are. So, what is the IQ range for a typical person?

What Is the IQ Range for a Typical Person?

IQ is commonly measured on a 200-point scale. Individuals scoring between 90 and 110 fall within the normal intellectual range; those scoring between 120 and 140 are considered bright or gifted; and those scoring above 140 are classified as geniuses. Lower scores indicate lower cognitive ability; individuals scoring below 70 are generally considered to have intellectual disability. IQ serves as a quantitative measure of human intelligence. This concept was first introduced in 1912 by German psychologist William Stern. The term “IQ” is the English abbreviation for “intelligence quotient.” Specifically, IQ is calculated as the ratio of mental age to chronological (physical) age, multiplied by 100. The formula for calculating IQ is as follows:

IQ = (Mental Age / Chronological Age) × 100. IQ reflects an individual’s cognitive ability—higher IQ scores indicate greater intellectual capacity. Chronological age refers to a person’s actual age since birth, whereas mental (or psychological) age represents the level of cognitive development assessed through standardized intelligence tests.

Later research revealed that, as people age, their cognitive abilities gradually decline. Consequently, using the ratio IQ method results in progressively lower scores with advancing age. To address this limitation, American psychiatrist David Wechsler proposed the concept of “deviation IQ.” The deviation IQ is calculated as follows: Deviation IQ = [(Raw Score − Mean Score for Age Group) / Standard Deviation for Age Group] × 15 + 100. Deviation IQ is considered more scientifically robust than ratio IQ because it remains relatively stable across the lifespan, even as chronological age increases.