Grade point averages and percentile systems are used by colleges and universities as baseline admissions guidelines. For example, a university law school program might require its applicants to hold a 3.5 undergraduate grade point average. Another university might require potential students to be in the 90th percentile of their high school or undergraduate class. However, a 3.5 GPA and a ranking in the 90th percentile could be completely different standards depending on the percentile scale used and the quality of education at specific schools.

Grade Point Average

A grade point average is a student's collection of grades over his academic career. GPAs are usually normalized on a scale of 0.0 to 4.0. For example, an A+ or an A corresponds to a 4.0, while an A- corresponds to a 3.7, a B+ equals a 3.3 and a B equals a 3.0. GPAs are individualized statistics. The primary difference between them and a percentile system is that they are not initially compared to the grades of other students, although they are often used for comparison purposes as raw data. For these purposes, raw data is numerical information not normalized onto a scale that compares students taking different courses. A high GPA is an excellent measure of academic ability because the student is being gauged personally against the classes he completed.

Percentile Systems

Percentile systems use a raw score, like a GPA or a standardized test score, and calculate how the score compares to the entire cohort of students. For example, the Princeton Review calculates a 3.7 GPA as being in the 92nd percentile of all college students. The student with a 3.7 GPA will most likely have an average better than 92 percent of the students in college. The Graduate Records Examination also uses a percentile system due to the sheer number of students taking the test. Students earn a raw score, which is calculated into a percentile rank. The Educational Testing Service transforms a raw score of 160 on the verbal and quantitative portion of the GRE into percentile scores of 84 for verbal reasoning and 78 for quantitative reasoning, respectively. In this case, a student scoring 160 on the GRE will be better than 84 percent of students in verbal reasoning and 78 percent of students in quantitative reasoning.

Percentiles as Supplementary Information

GPAs are the primary means to determine a student's academic ability, but percentiles are also used to compare students from different areas. A high school student with a 3.4 GPA could be more proficient than a student with a 3.7 GPA if the first student is in a higher percentile of her high school class than the second student. College admissions requirements often include a preference for students who rank in the top 10 or 20 percent of their class, which is in itself a percentile system, because grades from all students in a specific class are being compared.

Which Is More Useful?

Grade point averages and percentile ranks are useful for different reasons. GPAs are raw scores that serve as the baseline for student ability. Percentile ranks help to normalize a large amount of data using a bell curve. Without the raw data, developing the percentile rank is impossible. For this reason, college and graduate admissions advisers review transcripts and investigate grades more thoroughly than standardized test scores, which are considered one important data point out of many.