Though the spectrum of IQ scores is wide at first glance, the majority of people score between 85 and 115. IQ scores are calculated by taking someone’s mental age (the age at which they operate) and dividing it by their chronological age (the age that they actually are), and multiplying the answer by 100. Therefore, if someone is capable of doing the work of a person who is thirteen (13), but they themselves are in reality only (10), their IQ would be 130, because (13/10) x 100 = 130.
Many studies looking into the correlation between age and intelligence note that, for most people, IQ remains rather stable throughout early and mid-adulthood, and often remains so until late-adulthood, when it is shown to decline slowly. That said, crystallized intelligence remains intact, only fluid intelligence seems to decline with old age. Knowing that, IQ in old age can be protected by practicing mental acuity and making sure to keep one’s mind active through reading, puzzles, games, and social activities.
According to the Stanford-Binet Intelligence Scale Fifth Edition, an average IQ score is any score within the range of 80-119, where scores closer to 80 are considered Low Average, and scores closer to 119 are considered High Average. Next, the range considered Superior is within 120-129, above which is the Gifted range, 130-145. However, being considered “smart” has more to do with one’s mastery of a certain subject; intelligence is a measure of someone’s ability to adapt themselves to new situations and figure out the best solution with what they know at the moment. With that, being intelligent and being smart are as closely connected as being a good driver and a good mechanic, just because someone knows how to drive a car doesn’t mean they know about what makes it work.