Your GPA (grade point average) is a credit-weighted average of your grades on a 4.0 scale. The "credit-weighted" part is what people miss: a grade in a 4-credit course counts more than the same grade in a 1-credit course. Here's how to work it out.
The 4.0 scale
Each letter grade maps to a number of grade points. This is the most common US unweighted scale:
| Grade | Points | Grade | Points |
|---|---|---|---|
| A / A+ | 4.0 | C | 2.0 |
| A− | 3.7 | C− | 1.7 |
| B+ | 3.3 | D+ | 1.3 |
| B | 3.0 | D | 1.0 |
| B− | 2.7 | D− | 0.7 |
| C+ | 2.3 | F | 0.0 |
The formula
For each course, multiply its grade points by its credit hours to get "quality points". Add the quality points across all courses, then divide by the total credits. In short: GPA = total quality points ÷ total credits.
A worked example
Say you took three courses: an A in a 3-credit class, a B in a 3-credit class, and an A− in a 4-credit class.
- A (4.0) × 3 credits = 12.0 quality points
- B (3.0) × 3 credits = 9.0 quality points
- A− (3.7) × 4 credits = 14.8 quality points
- Total = 35.8 quality points ÷ 10 credits = 3.58 GPA
Weighted vs unweighted GPA
An unweighted GPA caps at 4.0 and treats every course's difficulty the same. A weighted GPA adds extra points for harder classes (honors or AP courses might use a 5.0 scale), so it can exceed 4.0. High schools often report weighted GPAs; most colleges use the unweighted 4.0 scale. The math is the same — only the point values per grade change.
GPA is a weighted mean, which is a cousin of the plain average — see mean vs median for how averages can mislead when values vary a lot.