Enter what you got right out of the total, and get your percentage and letter grade.
Results computed in your browser.
Once your percentage is calculated, it gets mapped to a letter using this scale, the same plus-and-minus cutoffs used elsewhere on this site:
These specific breakpoints, 93 for an A rather than 90, are one common convention among several. Some schools use a flat 90/80/70/60 scale with no plus or minus steps at all, and some curve every test individually. If your result's letter doesn't match what your teacher marked, that is very likely a different scale, not a bug in the arithmetic.
The core calculation is questions correct divided by total questions, times 100. If you enter a penalty per wrong answer, that penalty gets subtracted from your raw correct count before the percentage is taken, then the result is floored at zero so a heavy penalty can't push your score below nothing. Only after that final percentage is set does the tool look up which letter-grade band it falls into.
Because the penalty is applied before the percentage, a small penalty on a test with very few wrong answers barely moves the letter grade, while the same penalty on a test where you missed many questions can drop you a full letter band.
With 42 correct out of 50 questions and no penalty, the raw score is 42, so the percentage is 42 ÷ 50 × 100 = 84.0%, which lands in the B range (83 to 86). Add a penalty of 0.25 per wrong answer with 8 wrong: the adjusted score becomes 42 minus (8 × 0.25) = 42 minus 2 = 40, giving 40 ÷ 50 × 100 = 80.0%, right at the B- boundary, a full plus-or-minus step lower than the unpenalized result for the same 8 wrong answers.
Some tests subtract a fraction of a point for every wrong answer to discourage random guessing. If your test does that, enter the penalty per wrong answer there; if it doesn't, which is most classroom tests, leave it at zero.
This tool applies one specific set of cutoffs. Some teachers use a 93 percent cutoff for an A instead of 90, some grade on a curve, and some round a 92.5 up to a 93. Compare the cutoff table on this page against your syllabus if the letter looks off.
No, the calculator floors the result at zero even if the penalty math would otherwise produce a negative percentage, since a real test score can't be less than nothing.
Yes, as long as you can express your score as a correct amount out of a total amount, the same division works whether that is questions, points, or any other unit your test is scored in.