๐ Grading Calculator: Test Score to Letter Grade
By Shihab Mia ยท Updated 2026-07-18
Quick chart: 20-question test
| Wrong | Score | Percent | Grade |
|---|
This grading calculator turns a raw score into a percentage and a letter grade in one step. In EZ grader mode you enter the total number of questions and how many were wrong (or correct), and it returns the percentage correct and the matching letter on the standard US A to F scale. Switch to points mode to divide points earned by points possible for essays, projects, or any weighted assignment. Every result updates instantly as you type, so a 20-question test with 3 wrong shows 85 percent and a B on load.
What is the Grading Calculator?
Grading comes down to a single fraction: the score you earned divided by the score that was available, expressed as a percentage. In a multiple-choice or short-answer test, that fraction is the number of correct answers over the total number of questions. If a student gets 17 of 20 questions right, the percentage is 17 divided by 20, which is 0.85, or 85 percent. The EZ grader shortcut most teachers use flips this around: you count how many were wrong instead of right, because on a mostly correct paper the wrong answers are faster to tally. Three wrong out of 20 leaves 17 correct, and this grading calculator lands the math in the same place at 85 percent.
Points-based grading works the same way but replaces the question count with point values. An essay marked 42.5 out of 50 is 42.5 divided by 50, which is 0.85, again 85 percent. This method is essential whenever questions are not worth the same amount, such as a rubric where the introduction is worth 10 points and the analysis is worth 40. You add up the points the work earned and divide by the total points the assignment was worth. The percentage that comes out feeds into exactly the same letter-grade scale as a question-based score, which is why a single grading calculator can cover quizzes, essays, and projects alike.
The letter grade is a band, not a formula. The standard United States scale assigns A to 90 to 100 percent, B to 80 to 89, C to 70 to 79, D to 60 to 69, and F to anything below 60. Many schools add plus and minus bands inside each letter, so 97 and above is an A plus, 93 to 96 is a plain A, and 90 to 92 is an A minus, with the same three-way split repeating for B, C, and D. These cutoffs are conventions, not laws, so always check your school or instructor policy, because some institutions use a 7-point scale, a 93-is-an-A scale, or a lenient scale where an A starts at 85 percent.
Where grading trips people up is at the edges and in the rounding. A score of 89.5 percent is a B on a scale that does not round, but an A minus at a school that rounds to the nearest whole percent first. Extra-credit questions can push a score above 100 percent, and partial credit on points-based work produces decimals such as 42.5 that must be handled consistently. A good grading calculator keeps the raw percentage visible alongside the letter so you can see exactly where a score sits relative to the next cutoff, which is often the difference between two grades that feel very far apart to a student.
Curving is a separate step that adjusts raw scores after the fact, usually when a test turns out harder than intended. The simplest method is a flat or linear curve, where the same number of points is added to every paper, often enough to lift the top score to 100. A square-root curve raises each score to a value near its square root times 10, which helps lower scorers more than high scorers, while a bell curve fits grades to a target distribution. Curving changes the input to the grading calculator, not the scale itself: you curve the raw percentage first, then read the letter from the same bands.
Because the exact cutoffs vary, treat any grading calculator result as a starting point rather than an official transcript grade. In the United States there is no single national grading law; the common 90-80-70-60 scale is a widely followed convention documented by sources such as the U.S. Department of Education (ed.gov) and individual district policies. Confirm the scale, the rounding rule, and whether plus and minus grades are used for the specific class before you record a final letter, and use this grading calculator to check borderline scores against the next band up.
When to use it
- Grading a stack of quizzes fast by counting only the wrong answers on each paper.
- Converting points earned on an essay or project into a percentage and letter grade.
- Checking whether a borderline score rounds up to the next letter before you record it.
- Letting students self-check a practice test and see the grade a given number wrong produces.
- Working out the letter grade for a rubric-scored assignment with unequal point values.
- Building a quick reference of how many wrong answers drop a test of any length to each grade.
How to use the Grading Calculator
- Pick a mode: EZ grader for question counts, or points for earned-over-possible scoring.
- In EZ grader mode, enter the total questions, then the number wrong or correct.
- In points mode, enter the points earned and the total points possible.
- Read the percentage and letter grade in the results panel, updated as you type.
- Use the quick chart or copy the result to record or share it.
Formula & method
Worked examples
A 20-question quiz with 3 answers wrong (the default view).
- correct = total minus wrong = 20 minus 3 = 17
- percentage = 17 / 20 = 0.85
- multiply by 100 to get 85 percent
- 85 falls in the 80 to 89 band, so the letter is B
Result: 85 percent, letter grade B
An essay marked 42.5 points out of a possible 50 in points mode.
- percentage = points earned / points possible = 42.5 / 50
- 42.5 / 50 = 0.85
- multiply by 100 to get 85 percent
- 85 sits in the 80 to 89 band, which is a B
Result: 85 percent, letter grade B
A 50-question exam with 5 wrong, then a 5-point flat curve.
- correct = 50 minus 5 = 45, so raw percentage = 45 / 50 = 90 percent
- apply a flat curve by adding 5 points to the percentage: 90 plus 5 = 95
- 95 falls in the 93 to 96 band on the plus and minus scale
- read the letter from the same bands after curving
Result: 90 percent raw (A-), 95 percent curved (A)
Percentage to letter grade (standard US scale with +/- bands)
| Percentage | Letter | Band |
|---|---|---|
| 97 to 100 | A+ | A range |
| 93 to 96 | A | A range |
| 90 to 92 | A- | A range |
| 87 to 89 | B+ | B range |
| 83 to 86 | B | B range |
| 80 to 82 | B- | B range |
| 77 to 79 | C+ | C range |
| 73 to 76 | C | C range |
| 70 to 72 | C- | C range |
| 67 to 69 | D+ | D range |
| 63 to 66 | D | D range |
| 60 to 62 | D- | D range |
| Below 60 | F | Failing |
Wrong-answer quick chart for a 20-question test
| Wrong | Correct | Percentage | Letter |
|---|---|---|---|
| 0 | 20 | 100% | A+ |
| 1 | 19 | 95% | A |
| 2 | 18 | 90% | A- |
| 3 | 17 | 85% | B |
| 4 | 16 | 80% | B- |
| 5 | 15 | 75% | C |
| 6 | 14 | 70% | C- |
| 7 | 13 | 65% | D |
| 8 | 12 | 60% | D- |
| 9 | 11 | 55% | F |
| 10 | 10 | 50% | F |
Same number wrong across common test lengths (percentage correct)
| Wrong | 10 questions | 25 questions | 50 questions | 100 questions |
|---|---|---|---|---|
| 1 | 90% | 96% | 98% | 99% |
| 2 | 80% | 92% | 96% | 98% |
| 3 | 70% | 88% | 94% | 97% |
| 4 | 60% | 84% | 92% | 96% |
| 5 | 50% | 80% | 90% | 95% |
| 10 | 0% | 60% | 80% | 90% |
Common mistakes to avoid
- Mixing up wrong and correct in EZ grader mode. The EZ grader counts wrong answers, so entering the number correct by mistake flips the score. On a 20-question test, 3 wrong is 85 percent but 3 correct is only 15 percent. Use the wrong or correct selector so the tool knows which you are entering.
- Assuming the cutoffs are universal. The 90-80-70-60 scale is the most common in the US, but plenty of schools use a 7-point scale, a lenient scale where an A starts at 85, or set an A at 93 and above. Always confirm the grading policy for the specific class before recording a final letter.
- Rounding before you should. A raw 89.5 percent is a B unless the policy says to round to the nearest whole number first, which would make it 90 and an A minus. Decide whether rounding applies and apply it consistently to every score, not just the borderline ones.
- Forgetting that points must share the same total. In points mode the denominator is the points the assignment was worth, not the number of questions. A 3-question essay worth 50 points is scored out of 50, not out of 3. Always divide earned points by total possible points.
- Curving the letter instead of the score. A curve adjusts the raw percentage, not the letter grade directly. Add the curve to the percentage first, then read the letter from the scale. Bumping a B to an A without recomputing the percentage skips the step that keeps grades consistent across a class.
- Ignoring partial credit and half points. Many tests award 0.5 or 0.25 for partial answers, which the EZ grader whole-question count cannot capture. When partial credit applies, switch to points mode and enter the exact earned points, including decimals, over the total possible.
Glossary
- Percentage score
- The score earned divided by the score possible, multiplied by 100. It is the number the letter grade is read from.
- EZ grader
- A grading shortcut where you count how many answers are wrong out of the total, rather than counting the correct ones.
- Letter grade
- A band such as A, B, or C assigned to a range of percentages on a defined scale rather than a single value.
- Grading scale
- The set of cutoffs that maps percentages to letters, such as the standard US 90-80-70-60 scale.
- Plus and minus bands
- Sub-divisions inside a letter, so a B splits into B+, B, and B- across the 80 to 89 range.
- Points possible
- The maximum score an assignment can earn, used as the denominator in points-based grading.
- Curve
- An after-the-fact adjustment that raises raw scores, such as adding a flat number of points or applying a square-root formula.
- Rounding rule
- The policy that decides whether a score like 89.5 is bumped up to a whole number before the letter grade is read.
Frequently asked questions
How do I calculate a grade from the number of questions wrong?
Subtract the wrong answers from the total to get the correct count, then divide by the total and multiply by 100. For 3 wrong on a 20-question test, that is 17 divided by 20, which is 85 percent, a B. The EZ grader mode above does this the instant you type.
What percentage is each letter grade on the standard scale?
On the common US scale, A is 90 to 100, B is 80 to 89, C is 70 to 79, D is 60 to 69, and F is anything below 60. Many schools add plus and minus bands, so an 84 percent is a B and an 88 percent is a B plus.
What is the difference between EZ grader mode and points mode?
EZ grader mode works from a question count, so you enter the total questions and how many were wrong or right. Points mode works from point values, so you enter points earned and points possible. Both produce the same percentage and letter grade; choose the one that matches how the assignment is scored.
How many can I get wrong on a 20-question test and still get an A?
Two wrong out of 20 is 18 correct, which is 90 percent and an A minus. One wrong is 95 percent, a solid A. Three wrong drops you to 85 percent, a B, so on a 20-question test the A range ends at two wrong.
What grade is 15 out of 20?
A score of 15 out of 20 is 15 divided by 20, which is 0.75, or 75 percent. On the standard US scale 75 percent is a C, and a C on the plus and minus scale.
Is 89.5 percent an A or a B?
It depends on the rounding rule. Without rounding, 89.5 percent is a B (or B plus), because A does not begin until 90. If the policy rounds to the nearest whole percent first, 89.5 becomes 90 and an A minus, so check whether your class rounds.
How do you curve a test grade?
The simplest curve is a flat curve: add a fixed number of points to every raw percentage, often enough to bring the top score to 100. Apply the curve to the percentage, then read the letter from the same scale. Square-root and bell curves help lower scorers more but need a formula.
What is a passing grade percentage?
In most US schools a D at 60 percent is the lowest passing grade, and anything below 60 is a failing F. Many colleges require a C, or 70 percent, to pass a course or count it toward a major, so confirm the passing threshold for your program.
Can a score go above 100 percent with extra credit?
Yes. If a student earns more points than the assignment was worth, points mode will show a percentage above 100 and an A. Enter the points earned including the extra credit and the total the assignment was nominally worth as points possible.
Does this calculator handle plus and minus grades?
Yes. It reports the full letter with plus and minus bands, so 91 percent shows as A minus and 88 percent as B plus. If your school uses whole letters only, ignore the sign and read just the base letter.