GPA is the weighted average of your course grades where each class's credit hours act as the weight. This article explains the formula, a common grade→GPA table, and a worked example.
GPA — the formula
Calculate GPA as the sum of each class's grade points multiplied by its weight (credit hours), then divide by the total credit hours. Using weights makes classes with more credits affect the GPA more.
Step 1 — total credits: add up all course credit hours: C = c1 + c2 + ... + cn
Step 2 — weight for class i: wi = ci / C
Step 3 — GPA (weighted average):
GPA = w1×g1 + w2×g2 + ... + wn×gn
where gi is the numeric grade-point for class i
and wi = ci / (sum of all credits)Common grade → GPA mapping
Different schools use slightly different tables. The table below is a commonly used mapping where letter grades correspond to numeric GPA values.
| Letter | Percentage Range | GPA |
|---|---|---|
| A | 94–100 | 4.0 |
| A− | 90–93 | 3.7 |
| B+ | 87–89 | 3.3 |
| B | 84–86 | 3.0 |
| B− | 80–83 | 2.7 |
| C+ | 77–79 | 2.3 |
| C | 74–76 | 2.0 |
| C− | 70–73 | 1.7 |
| D+ | 67–69 | 1.3 |
| D | 64–66 | 1.0 |
| D− | 60–63 | 0.7 |
| F | 0–59 | 0.0 |
Note: Confirm your institution's exact grade mapping — some schools use different percentage bands or include plus/minus variations.
Worked example
Three classes:
- Class A: 2 credits, grade = A → g1 = 4.0
- Class B: 1 credit, grade = C → g2 = 2.0
- Class C: 1 credit, grade = C → g3 = 2.0
Total credits: 2 + 1 + 1 = 4
Weights:
- w1 = 2 / 4 = 0.5
- w2 = 1 / 4 = 0.25
- w3 = 1 / 4 = 0.25
GPA:
GPA = 0.5×4.0 + 0.25×2.0 + 0.25×2.0 = 2.0 + 0.5 + 0.5 = 3.0Tips & variations
- Some schools use a 5.0 or 12.0 scale — always check your institution's scale before converting percentages to grade points.
- Honors, AP, or graduate courses are sometimes weighted (e.g., +0.5 or +1.0). If weights are applied to grade points, include that adjustment when computing gi.
- To compute a running GPA, include all completed courses and their credits in the totals.
If you want, I can turn this into a downloadable standalone HTML file, add a calculator that computes GPA automatically, or adapt the grade table to match your school's scale.
