I use percentages to map to letter grades. The percentages mirror the 4.0 scale, except that where a GPA difference of 1.0 corresponds to a full letter grade, I use a percentage difference of 10. The table below shows the conversion from numerical grades to letter grades.
Number → Letter Conversion |
|
---|---|
Numerical Grade |
Letter Grade |
≥ 97.5 |
A+ |
≥ 92.5 |
A |
≥ 90.0 |
A- |
≥ 87.5 |
B+ |
≥ 82.5 |
B |
≥ 80.0 |
B- |
≥ 77.5 |
C+ |
≥ 72.5 |
C |
≥ 70.0 |
C- |
≥ 67.5 |
D+ |
≥ 62.5 |
D |
≥ 60.0 |
D- |
< 60.0 |
E |
Letter → Number Conversion |
|
---|---|
Letter Grade |
Numerical Grade |
A+ |
98.75 |
A |
95.00 |
A- |
91.25 |
B+ |
88.75 |
B |
85.00 |
B- |
81.25 |
C+ |
78.75 |
C |
75.00 |
C- |
71.25 |
D+ |
68.75 |
D |
65.00 |
D- |
61.25 |
E |
55.00 |
It is my practice not to round the numerical grade before mapping to letter grades by the table. This can be a sore point, so let me explain. For example, I use ≥90.00 as the transition from a B+ to an A-. This means that if your numerical grade is 89.9, I map it to a B+ and not an A-. It can be heartbreaking to miss a grade boundary by -0.1, I know. But to round up, say, every numerical grade ≥89.50 to 90.00 and map that to an A-, means that the transition from B+ to A- is actually 89.50, not 90.00. And that would mean that a grade of 89.4 would miss a grade boundary by -0.1. (It would also mean that me announcing the grade boundary of 90.00 is not accurate.) No matter what policiy is followed, some could miss a grade boundary by a hair. Even though there may be some psychological difference between the two situations, I prefer to keep it straightforward by announcing the sharp grade boundary and then following it strictly. I find it helps keeps the process more objective, and does not allow room for subjective grade adjustments, which are almost always unfair.