Most teachers will give you periodic updates on your grades throughout the year, letting you know what your final grade would be if the class ended right then and there. But you can figure the same information for yourself by finding the average of two or more grades or, to use the proper statistical term, the mean value. There's just one catch: The grades have to be in number form.
TL;DR (Too Long; Didn't Read)
Add the two grades together, then divide the result by two. The result is the mean value or average of the grades.
Averaging Two Percentage Grades
Often, you'll receive your grades as percentages. Let's say you scored 90 percent on one test, but struggled on the other and got a score of 72 percent. To average the two scores, first add them together: 72 + 90 = 162 percent. Next, divide that result by the number of scores involved (in this case, two) to get the mean value or average: 162 ÷ 2 = 81 percent. Note that you must carry the unit of measure over through every step of the calculation. Otherwise, you won't know how to interpret the result.
In order to average two grades, they must use the same unit of measure. For example, you can't average one grade that uses points and another that uses percentages. You must first convert them to the same unit of measure. Also, if you're averaging two scores based on points, for example, you got 15 out of 20 points possible on a test, and 2 out of 5 points possible on a pop quiz, each score must be out of the same number of points possible. In this case, you can't average the test score and the pop quiz score directly. But you can convert those "points out of..." scores into percentages, then average those percentages directly.
Averaging Letter Grades as Points
You can find the average of two letter grades, too, as long as you convert them into numbers first. The following, long-established system assigns a point value to each letter grade:
- A = 4 points
- B = 3 points
- C = 2 points
- D = 1 point
- F = 0 points
So if you had an A in one class and a B in one class, you'd convert that to 4 points (for the A) and 3 points (for the B). Then do the same calculation as for averaging any other number grade. First, add the two grade values together: 4 + 3 = 7 points. Then divide by the number of grades in the calculation (in this case, two). That leaves you with 7 ÷ 2 = 3.5 points as your average score. Some systems would convert that into a B+ or A-, but usually these points-for-grades scores, also known as your grade point average, are simply left in points form.
Averaging More Than Two Scores
You can use the same formula to calculator the mean value of more than two scores. Simply add all the scores together, then divide by the number of scores you used.
So if you took four tests throughout the year, getting 78, 93, 84 and 89 percent as your scores, first add them together: 78 + 93 + 84 + 89 = 344 percent. Then divide by the number of scores you used (in this case, four) to find your average or mean score: 344 ÷ 4 = 86 percent.
- Record all test results as they are received. Each time a new result is added, you can recalculate the average to keep it current.
- If one of the grades represents a test result that is of increased importance and the instructor wants to weight it accordingly, you must determine the relative weighting before you can calculate the average. For example, an exam is weighted more heavily than a quiz.
About the Author
Lisa studied mathematics at the University of Alaska, Anchorage, and spent several years tutoring high school and university students through scary -- but fun! -- math subjects like algebra and calculus.