The Armed Forces Qualification Test (AFQT) is composed of four components from the Armed Services Vocational Aptitude Battery (ASVAB). An individual's knowledge, aptitude, and reactions under stress can be determined by the ASVAB itself, while the AFQT is a metric used to determine suitability for a military career. The difference between the ASVAB and AFQT is that the former can provide an individual with information about what types of careers he might be well suited to, while the latter is specifically used to determine whether someone can be considered for service in the United States military.
In the United States, the military administers the ASVAB through a division known as the Military Entrance Processing Command. This battery of tests is often taken by high school students, though it is also open to older people that are otherwise eligible for enlistment. The primary purpose of the ASVAB is to determine suitability for military service, though it can also reveal aptitude for other endeavors. Some branches of the military began using the ASVAB and AFQT in 1968, and all branches had embraced it by 1976. It has undergone revisions since then.
There are about nine different sections in the ASVAB, and AFQT results depend on only four of them. Sections are added or removed from time to time, though the AFQT tends to depend on the core subjects of math, reading comprehension, and vocabulary. The math sections of the ASVAB are broken into mathematical knowledge and reasoning components, both of which are used to calculate the AFQT.
A percentile system is used to score the ASVAB and AFQT, and a 50 represents a score that is better than precisely half of test takers and worse than the other half. The formula for calculating the AFQT score is a little more complex, though it involves the ASVAB scores obtained for mathematic knowledge and reasoning, vocabulary, and reading comprehension. Each armed service requires a different score to be considered for enlistment, though they tend to range between 31 and 55. Some of the branches require a higher score for applicants that have general education development (GED) degrees instead of high school diplomas.
The ASVAB and AFQT can both be used to judge general aptitude, though only the latter is actually required to enlist in the United States military. Many high school students take the ASVAB simply to determine their aptitude for a variety of civilian occupations and will never use the AFQT score for anything. In other cases the AFQT score is very important, since it is one of the main points considered when determining whether someone can enlist.