How to Calculate an Exam Score
Converting a raw score into a percentage is simple arithmetic, but it's easy to make small mistakes under pressure, especially with odd totals like 23 or 37 questions. This calculator does the division for you and also answers the question most students actually have afterward: how many questions can I afford to get wrong next time?
The formula is the same one used by nearly every grading system: percentage = (questions correct ÷ total questions) × 100. The same formula works for points on free-response exams — use total points earned in place of questions correct.
Worked Example — Finding Your Score
Problem: You got 37 questions right out of 45 on a quiz. What's your percentage and letter grade?
Percentage: 37 ÷ 45 × 100 = 82.2%
On the common 10-point scale, 82.2% falls in the 80–89 range: Grade B.
Worked Example — Finding How Many You Need
Problem: A test has 60 questions. You want at least 85%. How many do you need right, and how many can you miss?
Needed correct: 0.85 × 60 = 51 (already a whole number, so no rounding needed)
You can miss up to 60 − 51 = 9 questions and still reach 85% (51/60 = 85.0%).
Why Rounding Matters
When the target percentage doesn't divide evenly into the total, the “questions needed” figure always rounds up — you can't answer a fraction of a question correctly. For a 50-question test and a 90% target, 0.90 × 50 = 45 exactly, so 45 correct is enough. But for a 47-question test, 0.90 × 47 = 42.3 — you'd need 43 correct, since 42 only reaches 89.4%.
This is also why the exact percentage you land on after rounding may be slightly above your target rather than exactly equal to it — that's expected, not an error.