The gap between a percentage score and a letter grade seems obvious until you're right at a boundary — is an 89.5% a B+ or an A−? The standard conversion scale used across most U.S. schools follows a consistent pattern, even though the exact cutoffs can vary slightly by institution.
Letter grades map to specific percentage ranges, typically in roughly 3-4 point bands, with plus and minus modifiers refining each letter grade further. While this is the most common scale, individual schools and instructors sometimes use different cutoffs, so it's always worth confirming against a specific syllabus when precision at a boundary matters.
The Standard Conversion Scale
93%+ = A | 90-92% = A− | 87-89% = B+ | 83-86% = B | 80-82% = B− | 77-79% = C+ | 73-76% = C | 70-72% = C− | 60-69% = D | Below 60% = F
A Worked Example
A score of 88 out of 100 points is 88% — falling in the 87-89% range, which converts to a B+. A score of 92.4 out of 100 rounds to 92%, landing at the top of the A− range (90-92%), just one percentage point from crossing into the straight A category at 93%.
Common Mistakes to Avoid
- Assuming every school uses identical cutoffs: some institutions use slightly different boundaries (an 89% might be a B+ at one school and an A− at another) — always check your specific syllabus.
- Rounding inconsistently near a boundary: a 92.5% rounding to 93% versus staying at 92% can mean the difference between an A− and an A — confirm your instructor's rounding policy.
- Confusing percentage score with GPA grade points: these are related but separate concepts — percentage-to-letter conversion is a different calculation from the letter-to-4.0-scale conversion used in GPA.
- Not accounting for weighted category averages before converting: if a course has weighted categories (homework, tests, participation), the final percentage needs to reflect that weighting before converting to a letter grade, not just a raw average of scores.
Bottom Line
Percentage-to-letter conversion follows a predictable scale, with school-specific variation near the boundaries. Use a Grade Calculator to instantly convert your points earned and total points into both a percentage and letter grade.