Teacher grader: what is the score?
Enter how many questions the test has and how many the student got wrong. The grader gives the percentage score and charts the score for any other number wrong.
- Score
- 85%
3 wrong out of 20 is a score of 85%.
- Number right
- 17
- Each question is worth
- 5%
Score: 85%. 3 wrong out of 20 is a score of 85%.
Score for each number wrong
How to calculate
An online EZ grader for teachers: turns the number of questions and the number a student got wrong into a percentage score, with the score for every other number wrong on a chart.
Example with the default inputs (Number of questions 20, Number wrong 3): 3 wrong out of 20 is a score of 85%.
Method: score = (questions − wrong) ÷ questions × 100; each question is worth 100 ÷ questions percentage points.
- Every question is worth the same. For a test with points, enter the total points as the number of questions and the points lost as the number wrong.
- The number wrong may be a fraction (half credit); it cannot be more than the number of questions.
- Questions are whole numbers from 1 to 1,000. The score is shown to one decimal place, rounded half up from the exact fraction.
Worked examples
Each example is checked against the calculator on every build.
- Number of questions 20, Number wrong 3 gives Score 85%, Number right 17, Each question is worth 5%.Source: OpenStax, Prealgebra 2e, §6.2 (percent = amount ÷ base × 100), https://openstax.org/books/prealgebra-2e/pages/6-2-solve-general-applications-of-percent
- Number of questions 30, Number wrong 7 gives Score 76.666667%, Number right 23, Each question is worth 3.333333%.Source: 23 ÷ 30 × 100 = 76.67 (percent method from OpenStax Prealgebra 2e §6.2, https://openstax.org/books/prealgebra-2e/pages/6-2-solve-general-applications-of-percent)
- Number of questions 25, Number wrong 2.5 gives Score 90%, Number right 22.5, Each question is worth 4%.
- Number of questions 8, Number wrong 1 gives Score 87.5%, Number right 7, Each question is worth 12.5%.
- Number of questions 40, Number wrong 0 gives Score 100%, Number right 40, Each question is worth 2.5%.
How it works
Every question is worth the same, so a student’s score is the share of the questions answered right:
score = (questions − wrong) ÷ questions × 100
Each question is worth 100 ÷ questions percentage points, so each question wrong takes that much off 100%.
The chart draws the score for every number wrong from 0 to the number of questions, and marks the number you typed.
Rules
- The number of questions is a whole number from 1 to 1,000.
- The number wrong is from 0 to 1,000 and may be a fraction for half credit (2.5). It cannot be more than the number of questions: "The number wrong cannot be more than the number of questions."
What the calculator shows
- Score: the exact value of (questions − wrong) ÷ questions × 100, shown as a percent rounded half up to at most one decimal place, without a trailing zero (85%, 76.7%).
- Number right: questions − wrong.
- Each question is worth: 100 ÷ questions, shown as a percent rounded half up to at most two decimal places, without trailing zeros.
The number wrong is read exactly as typed (2.5 is 5/2), so every value is an exact fraction before it is rounded to show.
Worked examples by hand
3 wrong out of 20. 20 − 3 = 17 right. Score: 17 ÷ 20 × 100 = 85%. Each question is worth 100 ÷ 20 = 5%.
7 wrong out of 30. 30 − 7 = 23 right. Score: 23 ÷ 30 × 100 = 76.666…, shown as 76.7%. Each question is worth 3.33%.
2.5 wrong out of 25 (half credit). 22.5 right. Score: 22.5 ÷ 25 × 100 = 90%. Each question is worth 4%.
1 wrong out of 8. 7 right. Score: 7 ÷ 8 × 100 = 87.5%. Each question is worth 12.5%.
0 wrong out of 40. Score: 100%. Each question is worth 2.5%.
Other questions people ask
How does an EZ grader work?
It divides the number of questions answered right by the number of questions and multiplies by 100. On a 20-question test, 3 wrong means 17 right, and 17 ÷ 20 × 100 = 85%. A paper EZ grader is a slide chart with these answers printed for each test length; this one works for any length up to 1,000 questions.
How do I grade a test with 30 questions?
Each question is worth 100 ÷ 30 = 3.33 percentage points. With 7 wrong, the student got 23 right: 23 ÷ 30 × 100 = 76.7%. The chart below the answer shows the score for every number wrong on the same test.
Can I give half credit?
Yes. Type a half as .5 in Number wrong. A student who lost 2.5 questions on a 25-question test scores (25 − 2.5) ÷ 25 × 100 = 90%.
What if the questions are worth different points?
Enter the total points as the number of questions and the points the student lost as the number wrong, as long as the total is a whole number. A 50-point test with 6 points lost scores 44 ÷ 50 × 100 = 88%.
How are scores rounded?
The score is shown to at most one decimal place, rounded half up from the exact value, so 7 wrong out of 30 shows as 76.7% and 1 wrong out of 8 as 87.5%. Many teachers then round to a whole percent, which would make 87.5% into 88%.
Which letter grade is my score?
That depends on your school’s grading scale. A common US scale gives an A for 90% to 100%, a B for 80% to 89%, a C for 70% to 79%, a D for 60% to 69% and an F below 60%, but many schools use other cut-offs, so the grader shows the percentage only.