The US Grading Scale, Explained
The most common US scale maps percentages to letters in 10-point bands, with plus/minus splitting each band. Your syllabus can override any of it — this is the default, not the law.
| Letter | Percent |
|---|---|
| A+ | 97–100% |
| A | 93–96.99% |
| A- | 90–92.99% |
| B+ | 87–89.99% |
| B | 83–86.99% |
| B- | 80–82.99% |
| C+ | 77–79.99% |
| C | 73–76.99% |
| C- | 70–72.99% |
| D+ | 67–69.99% |
| D | 63–66.99% |
| D- | 60–62.99% |
| F | below 60% |
Where the 10-point scale came from
The 90/80/70/60 banding became the de-facto US standard in the 20th century because it made mental math easy in a 100-point world. Plenty of alternatives exist — 7-point scales at some universities (93/85/77…), pure curve-based grading, and competency scales that skip letters entirely. When your class uses one of those, the percentages here won't match, but the calculators still will: they work from whatever cutoffs you have.
Worth knowing
Confirm the scale in your syllabus
The 90/80/70/60 letter cutoffs used here are the most common US scale, but plenty of courses curve, use plus/minus bands differently, or set an A at 94. The syllabus — not any calculator — is the contract that counts.
Percent and points are different animals
In a points-based course (600 points total), losing 12 points early costs the same as losing 12 late. In a weighted course, identical scores can move your grade differently depending on the category. Know which system you're in before doing mental math.