How to read the chart
Each row is a band, not a single value. On the plus/minus scale a B+ covers everything from 87 up to 89.99 — an 87.0 and an 89.9 are the same letter and carry the same 3.3 GPA points. That is why chasing the last two points inside a band changes nothing, and why crossing a boundary by a tenth changes a great deal.
The GPA column is per course. To turn several courses into one number you weight by credit hours, which is what the GPA calculator does — a 4-credit A pulls twice as hard as a 2-credit A.
The two scales, side by side
The same percentage maps to different letters depending on which scale you are on, and the gap is widest in the middle of each band:
| Percentage | Plus / minus | Straight letter |
|---|---|---|
| 95% | A (4.0) | A (4.0) |
| 91% | A- (3.7) | A (4.0) |
| 88% | B+ (3.3) | B (3.0) |
| 81% | B- (2.7) | B (3.0) |
| 78% | C+ (2.3) | C (2.0) |
| 71% | C- (1.7) | C (2.0) |
Notice it cuts both ways. A 91% is worth more on a straight scale (4.0 rather than 3.7), while an 88% is worth more on plus/minus (3.3 rather than 3.0). Plus/minus rewards consistency near the top of a band and punishes sitting just below one; straight-letter does the opposite. Neither is generous overall.
Rounding, and why it decides more than it should
An 89.5% is an A- at a school that rounds, a B+ at one that truncates. Across a semester that is 0.3 GPA points on a single course. Instructors are usually explicit about it in the syllabus precisely because it comes up so often — and if yours is not, it is a reasonable question to ask in week one rather than week fifteen.
The related trap is assuming your gradebook rounds the way your instructor does. Learning management systems display a rounded figure while storing the exact one, so an 89.5 shown as 90 may still be recorded as 89.5 when final grades are computed.
Converting the other direction
Going from GPA back to a percentage does not work cleanly, and it is worth knowing why. A 3.0 cumulative GPA is an average of letters, and letters are bands — a student with straight Bs and a student alternating As and Cs both land on 3.0 while having very different percentage records. Any "GPA to percentage" conversion is an approximation, and international credential evaluators treat it as one.
What you can do reliably is the forward direction: work out your percentage in each course, convert each to a letter using the chart above, and then average the points by credit hours. To get the percentage in a course still in progress, use the weighted grade calculator or the points-based calculator, depending on how your syllabus is structured.