How to calculate a test grade
One quick sum turns marks into a percentage, and a percentage into a letter. Here it is, plus the shortcut for counting wrong answers.
Turn questions answered correctly into a percentage and letter grade.
Working out a test grade is one of the quickest sums in school: it turns the marks you got into a percentage, and that percentage into a letter. Whether you are a student checking your own paper or a teacher grading a stack of them, the method is the same, and there is a handy shortcut when it is easier to count the ones that are wrong.
The test grade formula
A test grade is simply the share of the available marks you earned, as a percentage. Divide the points you earned by the total points possible, then multiply by 100:
Grade % = (points earned ÷ points possible) × 100
Say a test is out of 50 and you scored 42. Your grade is 42 ÷ 50 = 0.84, times 100 = 84%. If every question is worth one mark, the points are just the number of questions: 18 right out of 20 is 18 ÷ 20 = 90%. That is the whole calculation. The only thing that changes from test to test is the two numbers you put in.
The shortcut: count the wrong ones
Often it is faster to count the questions you got wrong than the ones you got right, especially on a long test with only a few mistakes. If so, subtract the wrong answers from the total and divide by the total:
Grade % = ((total − wrong) ÷ total) × 100
On a 40-question test with 7 wrong, that is (40 − 7) ÷ 40 = 33 ÷ 40 = 82.5%. It gives exactly the same answer as counting the right ones, just with less counting. Teachers grading quickly often work this way, counting the handful of errors on each paper rather than every correct answer across a whole class.
Turning the percentage into a letter grade
Most schools map the percentage onto a letter using bands. A common scale, used in the US, is:
A: 90 to 100%
B: 80 to 89%
C: 70 to 79%
D: 60 to 69%
F: below 60%
Many schools split these further with pluses and minuses (an A− at 90 to 92, a B+ at 87 to 89, and so on). So our 84% is a B, and 90% is an A. The important thing to know is that these bands are not universal: they vary by school, country and course. In the UK, for instance, 40% is often the pass mark and university degree classes use their own bands (70% and up for a first); many countries grade on a 1-to-7 scale or out of 20 entirely. Always check the scale on your own syllabus rather than assuming the US bands.
What about a curve?
Sometimes a teacher adds a curve, a few marks added to everyone's score to adjust a hard test. If your test was curved, add the curve to your points before you divide. A raw 85 out of 100 with a 5-point curve becomes 90 out of 100, which is 90%, an A instead of a B. The curve is applied to the points, not to the final percentage.
When questions are not worth one mark each
On many tests, questions carry different marks: a short question might be worth 2 marks and a long one 10. That changes nothing about the method, as long as you add up the actual marks rather than the number of questions. Total the marks you earned across every question, divide by the total marks the paper was worth, and multiply by 100. If you got 2 out of 2 on one question, 7 out of 10 on another and 5 out of 8 on a third, that is 14 marks earned out of 20 possible, which is 14 ÷ 20 = 70%. Counting questions only works when every question is worth the same; when they are not, count marks.
A quick reference table
For common test lengths, here is what each score works out to. It is just the formula applied, but it saves the arithmetic when you are grading by hand:
| Out of 10 | Out of 20 | Out of 50 | Grade |
|---|---|---|---|
| 9 | 18 | 45 | 90% (A) |
| 8 | 16 | 40 | 80% (B) |
| 7 | 14 | 35 | 70% (C) |
| 6 | 12 | 30 | 60% (D) |
The pattern is the same whatever the test is out of: the percentage is the score as a share of the total, so 16 out of 20 and 40 out of 50 are both 80%.
Rounding and borderline scores
A percentage often comes out with decimals, like 82.5% or 86.67%, and most schools round to the nearest whole percent before applying the letter band. A score that lands right on a boundary, say exactly 90%, is usually counted as the higher grade, but policies differ, so a mark sitting on the line between two letters is worth checking against your school's rule rather than assuming. If one or two marks would change your letter, it is also worth making sure every question was added up correctly. Extra credit works like a curve: add the extra points to your score before dividing, which can push the percentage above 100%.
What score do I need for a given grade?
You can run the formula backwards to find the marks you need. Multiply the grade you want by the total and divide by 100: to score 90% on a test out of 50, you need 90 × 50 ÷ 100 = 45 marks. To just pass at 60% out of 40, you need 60 × 40 ÷ 100 = 24. This is handy before a test to set a target, or to see how many you can afford to get wrong: 45 out of 50 means five marks to spare. To turn marks into a percentage either way without the arithmetic, the percentage calculator does it in one step.
One test is not your course grade
A single test grade tells you how you did on that test, not your overall standing in the class. Most courses weight different parts, so a 50%-weighted final matters far more than a 5% quiz. To combine several results into your current class grade, you weight each one, which is a different calculation covered in our guide on how to calculate a weighted grade. And if you want to know what you must score on a test still to come, see what grade do I need on my final.
The bottom line
A test grade is points earned divided by points possible, times 100, then matched to a letter band. Count the wrong answers instead when that is quicker, add any curve to the points first, and remember the letter bands differ between schools. To grade a stack of tests or check your own in a second, put the score into our test grade calculator, which shows the percentage and the letter at once; for combining results across a whole course, the grade calculator handles the weighting. If turning marks into percentages trips you up, our explainer on how to work out a percentage covers the basics.
Frequently asked questions
How do I calculate my test grade?
Divide the points you earned by the total points possible, then multiply by 100. A score of 42 out of 50 is 42 divided by 50, times 100, which is 84%. If each question is worth one mark, just divide the number right by the total number of questions.
How do I work out a grade by counting wrong answers?
Subtract the number wrong from the total, then divide by the total and multiply by 100. On a 40-question test with 7 wrong, that is (40 minus 7) divided by 40, which is 82.5%. It gives the same answer as counting the right ones, with less counting.
What letter grade is my percentage?
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 below 60%, often split further with pluses and minuses. These bands vary by school and country, so check your own syllabus; some use different cut-offs or a 40% or 50% pass mark.
How does a curve change my test grade?
A curve adds marks to everyone's score to adjust a hard test. Add the curve to your points before dividing. A raw 85 out of 100 with a 5-point curve becomes 90 out of 100, which is 90%. The curve is applied to the points, not to the final percentage.
Is a test grade the same as my course grade?
No. A test grade is just that one test. Your course grade usually combines several parts with different weights, so a heavily weighted final counts far more than a small quiz. Combining them is a weighted-grade calculation, which is a separate step from grading a single test.