**A student can calculate a semester grade by averaging the grades in the two previous quarters.** However, in some cases, the semester grade may include the grades from the previous two quarters and an exam. Typically, in this scenario, each quarter is worth 40 percent of the semester grade, and the exam is worth 20 percent. However, teachers and institutions can change this formula.

If the semester grade is the average of two quarter grades, the student has to add these two numbers together and divide by two to find the semester grade. If the student received an 80 percent in the first quarter and a 100 percent in the second quarter, the semester grade would be (80+100)/2 which equates to 90 percent.

If the quarter grades are written as letters, the person calculating the semester grade needs to convert those letters to numbers. Traditionally, A=4, B=3 and so forth. Therefore, if the student earned an A in the first quarter and a C in the second quarter, the semester grade would be a B. If the grade was a B in the first quarter and an A in the second quarter, the grade would be an A- or a B+. The average of 3 and 4 (the B and A grades listed above) is 3.5, and schools vary in whether they assign an A- or a B+ to this number.