Gather your high school transcripts and organize them by year, beginning with your freshman year.
Convert all final grades from your freshman year to numerical values. All As get four points, Bs get three points, Cs get two points and Ds get one point.
Add the numerical values and divide by the number of courses you took in your freshman year. For example, if you had four As and two Bs your freshman year, you would perform the operation 4+4+4+4+3+3 to get 22. Dividing 22 by 6 gives you 3.67. This is your unweighted GPA for that year.
Convert all of the grades into unweighted GPAs for your sophomore, junior and senior years following the same process. Often colleges want to see each year individually because it shows trends in your academic performance. For example, if your freshman GPA was a 2.5 and your senior GPA was a 3.5, this difference indicates you improved your academic performance over your high school career.
Add your GPAs from each of your four years of high school. Divide this number by four. This value is your cumulative unweighted GPA.