How a GPA is built
A GPA is a weighted average where the weights are credit hours. Each course converts its letter to grade points, multiplies by its credits to give quality points, and the GPA is the sum of quality points over the sum of credits. Nothing else. A term of a 4-credit A, a 3-credit B+, a 5-credit C and a 1-credit A− is (4.0 × 4) + (3.3 × 3) + (2.0 × 5) + (3.7 × 1) = 16 + 9.9 + 10 + 3.7 = 39.6 quality points over 13 credits, which is a 3.05 GPA.
Swap those same four letters onto four equal 3-credit courses and the GPA rises to 3.25, because the C is no longer carrying five of the thirteen credits. The letters did not change; the weights did. That is the whole reason a GPA calculator needs credit hours and cannot be built from letters alone.
The common 4.0 scale
| Letter | Grade points | Percentage band on a plus/minus scale |
|---|---|---|
| A | 4.0 | 93% and above |
| A- | 3.7 | 90% to under 93% |
| B+ | 3.3 | 87% to under 90% |
| B | 3.0 | 83% to under 87% |
| B- | 2.7 | 80% to under 83% |
| C+ | 2.3 | 77% to under 80% |
| C | 2.0 | 73% to under 77% |
| C- | 1.7 | 70% to under 73% |
| D+ | 1.3 | 67% to under 70% |
| D | 1.0 | 63% to under 67% |
| D- | 0.7 | 60% to under 63% |
| F | 0.0 | 0% to under 60% |
How far one course can move your GPA
This is the question behind most GPA searches, and the answer is unwelcome: less and less as you go on. The table below takes a student holding a 3.50 cumulative GPA and adds a single 3-credit course at each grade. The only thing that changes between rows is how many credits the student had already banked.
| Credits already earned | A (4.0) | B (3.0) | C (2.0) | D (1.0) | F (0.0) | Swing |
|---|---|---|---|---|---|---|
| 15 | 3.58 | 3.42 | 3.25 | 3.08 | 2.92 | 0.67 |
| 30 | 3.55 | 3.45 | 3.36 | 3.27 | 3.18 | 0.36 |
| 45 | 3.53 | 3.47 | 3.41 | 3.34 | 3.28 | 0.25 |
| 60 | 3.52 | 3.48 | 3.43 | 3.38 | 3.33 | 0.19 |
| 90 | 3.52 | 3.48 | 3.45 | 3.42 | 3.39 | 0.13 |
| 120 | 3.51 | 3.49 | 3.46 | 3.44 | 3.41 | 0.10 |
A first-year student 15 credits into a degree moves between 3.58 and 2.92 on one course — a swing of 0.67, which is the difference between two very different-looking transcripts. The same course taken at 120 credits moves the same student between 3.51 and 3.41: a swing of 0.10. The lever has a closed form, incidentally — the swing is 12 ÷ (credits + 3), because four grade points times three credits is twelve quality points, spread over the new total.
Two things follow. Early courses matter far more than they feel like they should, including the 1-credit ones nobody takes seriously in a first semester. And a low cumulative GPA late in a degree cannot be repaired quickly by arithmetic — it takes a large number of credits, not a heroic term. If you are reading this in August with a term about to start, the useful move is to enter the term you are about to take with plausible grades and see the cumulative figure it produces. That number is a plan; the same number computed in December is a report.
Working backwards to a target
The algebra is the same as the final-exam case. Say you hold 45 credits at 3.20 — that is 144 quality points — and you want a 3.40 cumulative after a 15-credit term. The target total is 3.40 × 60 = 204 quality points, you already hold 144, so the term must supply 60 quality points over 15 credits: a term GPA of 4.00 exactly. In other words, that particular target requires a perfect term, and knowing so in advance is worth more than discovering it in January. If the required figure comes out above 4.0, the target is not reachable this term at all, and the honest next question is how many terms it would take.
Related calculators
- Grade calculator — get the course percentage right before you turn it into a letter and a grade point.
- Final grade calculator — the same "what do I need" algebra, one level down, inside a single course.
- Semester grade calculator — combine quarter grades and a final exam into the semester grade that becomes the letter on your transcript.