The standard US grading scale
US grading scale: 90-100% is A, 80-89% is B, 70-79% is C, 60-69% is D, and below 60% is F. That is the whole scale, and it is the default used on this site. A percentage tells you how many marks you earned; the letter tells you which band that percentage falls in.
| Percentage | Letter grade |
|---|---|
| 90-100% | A |
| 80-89% | B |
| 70-79% | C |
| 60-69% | D |
| Below 60% | F |
Read it as a band, not a single number. An 85% and an 89% are both B, and a 91% and a 99% are both A. The letter hides the exact percentage, which is why you should keep the percentage alongside it whenever the exact score matters.
Worked examples: percentage to letter grade
Convert points to a percentage first, then read the letter from the scale above. The formula is points earned ÷ points possible × 100.
- 20 questions, 3 wrong: 17 ÷ 20 × 100 = 85% → B.
- 50 questions, 7 wrong: 43 ÷ 50 × 100 = 86% → B.
- 30 questions, 2 wrong: 28 ÷ 30 × 100 = 93.3% → A.
Try any of these on the Grade Calculator – enter the total and the number wrong, and the percentage, letter and grading chart update together, so you can see exactly where a score sits.
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Why the boundary matters most
Most grading-scale mistakes happen at the edges, not in the middle of a band. 89% is still a B, not an A. 90% is the first A. 59% is an F, 60% is the first D. 69% is a D, 70% is the first C. If you are one mark from the next letter, that one mark is worth checking: on a 20-question test, one more correct answer moves 85% (17/20) to 90% (18/20) – a whole letter, not a small change.
That is also why a grading chart for teachers is useful as a reference, not just a calculator result. A chart shows every wrong-answer count and its letter at a glance, so a teacher marking a stack of papers can see borderline scores without re-doing the division for each paper.
Why your school’s scale may differ
Not every school uses 90/80/70/60. Some use plus and minus grades (A-, B+), some set A at 93%, and some grade on a curve. Always check your own syllabus first: if your school’s A starts at 93%, then a 91% is a B there even though it is an A on the standard scale above.
That is why the scale on this site is editable. On the Grade Calculator homepage, open “Change the grade scale (optional)” and move the A, B, C and D cut-offs – for example, from 90 to 93 – and the letter updates everywhere on the page, including the chart. The percentage never changes; only the letter it maps to does.
Percentage, letter and weighted grades – not the same thing
A letter grade is a band, not a number, and it should not be averaged as if A, B and C were equally spaced. If you have several grades with different weights, convert each one to its percentage first, then weight the percentages. That is exactly what the Average Grade Calculator does in Percentage, Letters or Points mode, and the worked weighted example there gives 84.57%, which sits in the B band on this scale.
If you need to work backwards from a target instead, use the Final Grade Calculator for example, 84% now with a 30% final and an 85% target needs 87.3% on the final, which is also a B on this scale – so a B target does not automatically mean a B on the final is enough.
Common mistakes with grading scales
- Treating 89% as an A. On the standard scale it is a B. The cut-off is the cut-off, however close the score looks.
- Assuming every school uses the same scale. Plus/minus grades and a 93% A are common. Check the syllabus, then set the tool’s cut-offs to match.
- Averaging letters directly. Convert letters to their percentages first, then average or weight those percentages.
- Rounding before converting. Keep the full percentage through the calculation and read the letter last; rounding 89.6% up to 90% before reading the band can change the letter on a technicality your school may not allow.
- Forgetting that a letter hides the exact score. An 85% and an 89% are both B, but they are not the same result. Keep the percentage with the letter.
Try it with your own grades
Put your own total and wrong answers into the Grade Calculator and check the letter against the scale above, then change the cut-offs to your school’s scale if they differ and watch the letter update. For a course average, use the Average Grade Calculator instead – it works from percentages, letters or points, and shows which assignment is moving your grade most.
Frequently asked questions
What percentage is an A?
On the standard US scale used as this site’s default, 90-100% is an A. Some schools set A at 93%, so check your syllabus – a 91% is an A on the standard scale but a B at a 93% school.
What letter grade is 85%?
85% is a B on the standard US scale (80-89%). For example, 17 out of 20 is 17 ÷ 20 × 100 = 85%, which is a B.
Is 89% an A or a B?
89% is a B on the standard scale. 90% is the first A, so 89% misses it by one percentage point, however close it looks.
Do plus and minus grades change the scale?
Yes, where a school uses them. A-, B+ and similar grades split the main bands into smaller ranges, and the exact cut-offs vary by school. Use your school’s published scale, and set the Grade Calculator’s cut-offs to match it, rather than assuming a universal plus/minus table.