How GPA works
Your Grade Point Average (GPA) converts letter grades into a single number so schools can compare performance across different courses and credit loads. It comes down to three steps.
1. Grades become points
Each letter grade maps to a point value on a scale — most commonly 4.0 for an A down to 0 for an F. Many schools also use plus/minus grades, worth roughly 0.3 more or less than the base letter.
2. Points become quality points
Multiply each course's grade points by its credit hours. A 4-credit course graded A- earns 3.7 × 4 = 14.8 quality points — a 1-credit course with the same grade only earns 3.7.
3. Quality points become your GPA
Add up quality points across every course, then divide by total credits attempted. That average is your GPA for the semester — or, across every semester you've taken, your cumulative GPA.
A worked example
Say you took two courses: a 3-credit course graded B (3.0 points) and a 5-credit course graded A- (3.7 points).
| Grade | Points | Credits | Quality points |
|---|---|---|---|
| B | 3.0 | 3 | 9.0 |
| A- | 3.7 | 5 | 18.5 |
Total quality points: 9.0 + 18.5 = 27.5. Total credits: 3 + 5 = 8. GPA: 27.5 ÷ 8 = 3.44 — closer to the A- than a simple 50/50 average of B and A- would suggest, because the A- carried more credits.
Semester GPA vs. cumulative GPA
The steps above work identically whether you're calculating one semester or your whole academic career — the only difference is which courses you include. A semester GPA uses just that term's courses; a cumulative GPA uses every course, every term, combined into one running average.
Frequently asked questions
Because courses aren't equal in size. A 4-credit course represents four times the coursework of a 1-credit course, so it should move your average four times as much. Weighting by credits is what makes that fair.
A percentage grade (like 91%) describes one assignment or one course. GPA is a weighted average of grade-point values across every course you've taken — the two measure different things and don't convert directly without knowing your school's percentage-to-GPA scale.
No. Most U.S. colleges use a 4.0 plus/minus scale, but some cap an A+ at 4.0 while others use 4.33. High schools often add weighting for Honors/AP courses on top of that. Always check your specific institution's published scale.
Most schools round the final GPA to two decimal places after dividing total quality points by total credits — not at each individual course. Rounding grade-by-grade before summing can shift the final number slightly, which is a common source of small discrepancies between calculators.