How this calculator works
The percentage is the number correct divided by the total, scaled to 100. If every question is worth the same, the number wrong is simply the total minus the number correct, and the same percentage follows from either count. A test marked out of points works the same way: 42 out of 50 and 84 percent are equivalent. The letter grade is then looked up on a standard percentage scale. Tests with a penalty for wrong answers, partial credit or questions of different value need a points-based weighted calculation instead.
Formula
percentage = number correct / total x 100. Number wrong = total - number correct. From a percentage, number correct = percentage x total. The letter scale is A+ 97, A 93, A- 90, B+ 87, B 83, B- 80, C+ 77, C 73, C- 70, D+ 67, D 63, D- 60, F below 60.
Worked example
A test with 50 points and 42 correct gives 42 / 50 = 84 percent, an 8 wrong and a B. If instead the teacher reports 8 wrong out of 50, the same calculation gives 42 correct and 84 percent. Checking a target of 90 percent on a 60-point test gives 0.90 x 60 = 54 correct and 6 wrong.
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Frequently asked questions
Does a wrong answer reduce the score by more than one point?
Not in this calculator. It assumes one point for a correct answer and no penalty for an incorrect one, which is common on school tests. A test that subtracts a quarter point for a wrong answer, such as some standardized exams, needs the raw scoring formula for that exam.
What if questions have different point values?
Use the grade calculator in points mode instead. Enter each section as points earned and points possible, and it will weight the sections correctly. This page is for a test where every question is worth the same.
How is the letter grade decided?
It uses a common percentage scale with plus and minus grades. Schools differ: some start an A at 90, others at 93, and some use whole letters only. The percentage is exact; the letter is a convention that your school or teacher may define differently.
Can the result be a fraction of a point?
Yes, when you start from a percentage. A 90 percent target on a 45-point test needs 40.5 correct, which is not a whole question. The result is shown to two decimal places so you can see whether rounding up or down is needed.