How I Calculate Grades

Dr. Stuart Blythe
Department of English & Linguistics
Indiana University - Purdue University Fort Wayne

During most courses, I assign numerical grades--from a single point applied to a small exercise to a couple dozen points applied to a large project. The total points any student earns is then translated at the end of the semester into a letter grade (i.e., A, B, C, D, F). If you are a student of mine, you may well ask, "How will my numerical grades be translated to a letter grade?" That question is addressed in this handout.

Why I use numerical grades

I use numerical grades during the semester for two reasons: greater flexibility and increased objectivity.

Numerical grades offer me greater flexibility because the practice allows for finer distinctions when evaluating student work. If I were to use letter grades, I could make one of only 15 summary evaluations (A+, A, A-, B+ ...). But if I were to use numerical grades, I could make many more distinctions. I could make over 50 distinctions, for example, if a project were worth 20 points. In such a case, A's would range between 18 and 20. If I were to use tenths of a point, I could make 20 distinctions within the A range alone (i.e., 18, 18.1, 18.2 ...).

Numerical grades also offer me a kind of objectivity by putting some distance between myself and the final letter grade. Over the course of a semester, students may earn points for such activities as in-class exercises, major projects, and peer reviews. All that adds up after a while. With so many points, I have difficulty figuring out how one set of points may contribute to a final letter grade, and I don't take the time to figure out the numbers until the end of the semester. As a consequence, I keep myself ignorant of how anyone's numerical score on any exercise or project may translate to a final grade. This keeps me focused on the merits of the product itself, rather than its effect on a final grade.

Although numerical grades offer several benefits, they do make the process of assigning letter grades seem a bit complicated. The trick is to convert numerical grades to letter grades, which I explain in the next section.

The dilemma: Translating grades from numbers to letters

When translating numerical grades to a letter grade, I must reduce numerous distinctions (say, between 18.1, 18.3, 18.5) to one of only five distinctions (A, B, C, D, F). Here's how I do that:

1. I grade on a percentage scale. I do not like grading on a curve because it dictates that some students must fail the course, which is unfair. I prefer to give each student an opportunity to earn the points available. If a student receives at least 90% of a total grade, then she should receive an A.
2. I convert exercise and review grades to get a final number of points. For example, a final exercise grade may be worth 20 points toward the final grade. But, as the semester progresses, students may earn up to 35 exercise points. How to get from 35 to 20?
1. I convert the actual points earned (35) to the final points available (20) by dividing the total earned by the total possible. Say a student earned 32.4 of 35 points. That would equal 0.93 (rounded up).
2. I multiply the result by the total possible for the final grade.
In the example here, I would multiply 20 by 0.93, which would equal 18.6. That 18.6 would be the student's final exercise grade.
3. Once I determine final numerical grades for all portions of the course, I determine each student's scores as a percentage of the total possible. Moreover, I do this to the nearest 10th of a point. For example, if students could earn up to 100 points in a semester, the grade would be calculated this way:

The truly difficult part in all this occurs when a student earns, say, a 79.7 out of 100. Of course, that would be very close to a B (80.0). Still, the cutoff must occur somewhere. Be warned: I tend to stick with the cut off numbers.

Questions?

Please contact me at 260-481-6089 or blythes@ipfw.edu.