A percentage and a GPA measure are related through a grading policy, not through one national formula. A 90 percent can be an A at one school and an A- at another. Some institutions do not convert percentages at all.
The defensible method
- Find the official percentage-to-letter table.
- Convert each final course percentage to its letter grade.
- Convert that letter grade to the school's grade points.
- Weight the points by course credits.
Example using one stated scale
Assume this example scale: 93 to 100 = A = 4.0, 90 to 92 = A- = 3.7, 87 to 89 = B+ = 3.3, and 83 to 86 = B = 3.0.
| Course | Percent | Letter | Points | Credits |
|---|---|---|---|---|
| English | 91% | A- | 3.7 | 1 |
| Biology | 88% | B+ | 3.3 | 1 |
| History | 94% | A | 4.0 | 1 |
Do not convert the overall average blindly
Converting one combined percentage can produce a different result from converting each course. GPA is usually course-based. A 92 in one class and an 84 in another may map to 3.7 and 3.0, even though their simple percentage average is 88.
International and application conversions
Do not use a US online table to rewrite an international transcript. Admissions offices and credential evaluators may have their own procedures. Enter grades as instructed by the receiving organization.
Pay attention to grade-band boundaries
Percentage conversion is discontinuous. Under the example scale, 89 maps to B+ at 3.3 while 90 maps to A- at 3.7. Dividing a percentage by a constant cannot reproduce that jump. This is why a linear shortcut such as percentage divided by 25 is not a defensible school GPA method.
When a final percentage contains decimals, apply the school's rounding rule before choosing the letter band. Do not round both the course percentage and the final GPA repeatedly.
Label the scale with the result
A useful estimate should say which percentage bands and GPA values were used. A bare result such as "91% equals 3.7" hides the most important assumption.