The formula for calculation of Intelligence Quotient (IQ) is:

Intelligence Quotient is abbreviated as IQ. IQ is a measurement of a person’s intelligence and it is measured in number. The average IQ of a person is 100.

In 1905, a French psychologist, Alfred Binet invented the first practical IQ test along with his Theodore Simon. The first IQ test was named as Binet-Simon Scale. 

Key Points

• Intelligence quotient (IQ) applies to mental age (MA) expressed as a ratio of chronological age (CA) multiplied by 100.

• In 1916, the revised version was published and named the Stanford-Binet Intelligence Scale. This test used a number of IQ. It provided a formula to measure the IQ that is dividing the person’s mental age by his chronological age and then multiplying the result with 100.

  Here, 100 is multiplied to avoid the fractions in the result of the division.

• For IQ to remain firm, MA must increase with CA over time.
• This is true until around 18 years when intellectual abilities are usually fully developed.
• As stated above, it was erroneously believed that intellectual ability started to decline after young adulthood.

Thus from the above-mentioned points, it is clear that the formula for calculation of Intelligence Quotient (IQ) is .