Easy grader calculator for teachers
You just finished grading thirty quizzes, and now comes the tedious part: turning each tally of wrong answers into a percentage and a letter, without slipping up and without losing your afternoon to a calculator.
- Step-by-step explanation of the math
- Worked examples included
- Faster than a spreadsheet
Easy grader calculator for teachers
Enter your numbers and press Calculate
How to use the easy grader calculator
The tool needs just two numbers and grades the test in one click:
1. Total questions: how many items the test had (for example, 25). 2. Wrong answers: how many the student missed (for example, 3).
From those it returns three things: the percentage score, the number of correct answers, and the letter grade on the US scale (A, B, C, D, F).
The percentage formula is straightforward:
score = (total questions − wrong answers) / total questions × 100
And the count correct is simply:
correct = total questions − wrong answers
The letter is assigned by band: 90% or above is an A, 80 to 89.9% is a B, 70 to 79.9% is a C, 60 to 69.9% is a D, and anything below 60% is an F.
Worked example: a 25-question test with 3 wrong answers.
- Correct: 25 − 3 = 22
- Percentage: 22 / 25 × 100 = 88%
- Letter: 88% falls in the 80–89.9 band, so the grade is a B.
To grade a whole stack of the same test, leave the total question count fixed and just change the number of wrong answers for each student: the calculator rebuilds the percentage and the letter instantly.
Worked grading examples
These cases run through the whole letter scale so you can see how the grade shifts with each wrong answer. The formula is always score = (total − wrong) / total × 100.
- 20-question test, 1 wrong (an A): correct = 20 − 1 = 19; score = 19 / 20 × 100 = 95%. Since 95% ≥ 90%, the letter is an A.
- 20-question test, 3 wrong (a B): correct = 20 − 3 = 17; score = 17 / 20 × 100 = 85%. 85% lands in the 80–89.9 band, so the letter is a B.
- 40-question test, 9 wrong (a C): correct = 40 − 9 = 31; score = 31 / 40 × 100 = 77.5%. 77.5% sits between 70 and 79.9, so the letter is a C.
- 50-question test, 20 wrong (a D): correct = 50 − 20 = 30; score = 30 / 50 × 100 = 60%. Right on the cutoff: 60% is a D, not an F, because the D band starts at 60%.
- 15-question test, 9 wrong (an F): correct = 15 − 9 = 6; score = 6 / 15 × 100 = 40%. Below 60%, so the letter is an F.
Notice the 60% edge case: one percentage point separates passing with a D from failing with an F. That is why it pays to compute the exact percentage instead of rounding in your head, especially when the question count is not a round number and each miss is worth an odd fraction (on the 15-item test, every wrong answer costs 6.67 points).
What an easy grader is and why teachers use one
The easy grader (or EZ Grader) started life as a cardboard wheel with two rotating disks: on one you picked the total number of questions, and on the other you read off the grade based on how many were wrong. It was a staple for generations of US teachers because it solves one concrete, repetitive problem: turning "5 wrong out of 30" into a percentage and a letter without doing the division by hand thirty times in a row. This calculator does exactly the same job, minus the cardboard wear and with exact decimals.
The logic is deliberately simple. The percentage grade is the share of correct answers over the total, and the letter follows the US ten-point scale: A for 90% or more, B from 80 to 89, C from 70 to 79, D from 60 to 69, and F below 60. That A–F scale is the reference in the United States; other systems map percentages differently, but the percentage the tool computes is universal, so you can translate it afterward into your own scale (out of 10, out of 20, pass/merit/distinction, and so on).
One important caveat: this calculator assumes every question is worth the same and that each wrong answer counts as zero. If your test weights some questions more heavily, awards partial credit, or penalizes errors differently, the raw share of correct answers is only a starting point. For those cases — averaging several grades, weighting by credits, or converting between scales — there are dedicated tools linked below. For the everyday task of grading a stack of identical tests, though, this is the calculation you need, and it does it in one click.
About this calculator
This tool is the digital version of the classic easy grader (the teacher's cardboard wheel): enter how many questions the test had and how many the student missed, and you instantly get the score percentage, the number of correct answers, and the matching letter grade (A, B, C, D, or F). The math is the same across a whole stack of the same test, so you only change the number wrong for each paper. It works with any number of questions (it doesn't have to be a multiple of ten) and spreads the decimals evenly, exactly what you need when a 40-item quiz has a student with 7 misses and you want the precise grade without eyeballing the rounding.
Frequently asked questions
How is the grade calculated from the number wrong?
The percentage is (total questions − wrong answers) divided by the total questions, times 100. For example, on a 30-question test with 5 wrong: (30 − 5) / 30 × 100 = 83.3%. Then the letter is assigned in ten-point bands: 90% or more is an A, 80–89% is a B, 70–79% is a C, 60–69% is a D, and under 60% is an F. You don't have to count the correct answers by hand; the total and the number wrong are enough.
What percentage matches each letter grade (A, B, C, D, F)?
The standard US scale uses ten-point bands: A is 90–100%, B is 80–89.9%, C is 70–79.9%, D is 60–69.9%, and F is anything below 60%. The passing threshold is usually set at 60% (the D). Some schools add plus/minus refinements (+ and −) or raise the passing bar to 65% or 70%, but this calculator applies the classic five-letter scale without signs, which is the most widely used.
Does it work if the test doesn't have a round number of questions?
Yes. The formula always divides by the real number of questions, whether that's 7, 23, or 100, so it doesn't have to be a multiple of ten. On a 23-question test with 4 wrong, the percentage is (23 − 4) / 23 × 100 = 82.6%, which is a B. The calculator shows the exact decimal; you then decide whether to round it when you copy it into your gradebook or your own grading scale.
Does it work for tests with partial credit or differently weighted questions?
This tool assumes every question is worth the same and that each wrong answer counts as zero, which is the typical case for a right/wrong quiz. If your test awards partial credit or weights some questions more than others, first convert the score earned into an equivalent count of correct answers and use that here, or reach for a percentage or weighted-average calculator. For the bulk of multiple-choice-style tests, though, the total-and-wrong calculation is exactly what you need.