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.

  \(IQ = \frac{{{\rm{\;}}Mental\;age}}{{Chronological\;age\;}}\; \times 100\)

  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 \(\frac{MA}{CA} \times 100\).