EZ Grader Chart Explained: How Teachers Grade a Whole Class in Minutes
Short answer: an EZ grader chart is a lookup table that turns “how many wrong” into a percentage and a letter grade — no division required.
Find the number of questions on the test, find how many answers the student got wrong, and read the grade straight across the row.
That one trick is how teachers have graded a whole stack of papers in minutes for generations, long before online calculators existed.
This guide explains what an EZ grader chart is, how the original cardboard slider worked, how to read a chart today, and the mistakes that cost teachers marks.
It also includes ready-to-use charts for the test sizes teachers actually set: 10, 20, 25, 50, and 100 questions.
What Is an EZ Grader Chart?
An EZ grader chart — sometimes written “E-Z Grader” — is a table built on a single formula:
Percentage = (total questions − wrong answers) ÷ total questions × 100
Every row of the EZ grader chart does that division once, in advance, for one possible number of wrong answers.
So instead of working out 17 ÷ 20 on a calculator for every paper, the teacher looks up the row for “3 wrong on a 20-question test” and reads 85%.
The EZ grader chart only fits one kind of test: questions that are all worth the same, marked right or wrong.
That covers most multiple-choice quizzes, spelling tests, exit tickets, and short objective tests — which is exactly why it became a classroom staple.
If questions carry different points, or some answers earn half credit, a chart alone is not enough, and you need a points-based tool instead (see Class Grade Calculator or the Weighted Grade Calculator).
The Original Cardboard Slider: How Teachers Graded Before Computers
Before the online version, the EZ grader was a physical object: a cardboard sleeve with a sliding insert inside it.
The teacher slid the inner chart until an arrow at the top pointed to the total number of problems on the test.
The windows cut into the sleeve then lined up with the right column of grades, and the teacher read down the “number of problems wrong” column to find each student’s percentage.
The classic Advantus E-Z Grader worked exactly this way: the front side of the chart handled tests of up to 50 problems, and the reverse side handled up to 95 problems.
Grades on the original chart were rounded off to the nearest whole percentage, giving the benefit of one-half — so a score of 89.5% read as 90%, not 89%.
That rounding rule still matters today, because it decides borderline grades (more on that below).
The slider sat in classroom desks across the US for decades because it solved a real problem: grading 30 papers by hand means 30 separate divisions, and every one is a chance to slip a digit.
The chart replaced all 30 divisions with 30 lookups. It was simple, fast, and it worked every time — which is why the idea survived the move to screens.
Today’s online Teacher Grader does the same job: type in the total and the number wrong, and the percentage and letter grade appear instantly, for any test size.
Read more about how the original chart worked in the Advantus E-Z Grader Chart user manual, which describes the slide-and-read method and the two-sided chart.
How to Read an EZ Grader Chart in 3 Steps
Step 1 — Find the right chart. Charts are built for one test size at a time.
A 20-question chart is useless for a 25-question quiz, because every wrong answer costs a different amount (5% on a 20-question test, 4% on a 25-question test). Always match the chart to the total first.
Step 2 — Count the wrong answers. Mark the paper, count how many answers are wrong, and ignore everything else. Do not count the right answers and work backwards — that is where most counting errors creep in.
Step 3 — Read across the row. Find the “wrong” number in the left column and read across to the percentage and the letter grade.
Write that grade on the paper and move to the next one. A whole stack goes quickly once the counting, not the maths, is the only work left.
The One Thing That Changes Everything: What Each Wrong Answer Costs
On a short test, every mistake is expensive. On a long test, the same mistake barely moves the grade.
This is the single most useful thing a chart teaches students — and the reason teachers choose test lengths carefully:
| Test size | Each wrong answer costs | 3 wrong = | 5 wrong = |
|---|---|---|---|
| 10 questions | 10% | 70% (C−) | 50% (F) |
| 15 questions | 6.67% | 80% (B−) | 66.67% (D) |
| 20 questions | 5% | 85% (B) | 75% (C) |
| 25 questions | 4% | 88% (B+) | 80% (B−) |
| 50 questions | 2% | 94% (A) | 90% (A−) |
| 100 questions | 1% | 97% (A+) | 95% (A) |
Letter grades use this site’s standard scale (A+ 97–100, A 93–<97, A− 90–<93, B+ 87–<90, B 83–<87, B− 80–<83, C+ 77–<80, C 73–<77, C− 70–<73, D+ 67–<70, D 63–<67, D− 60–<63, F below 60).
Note: letter grades depend on your school’s own scale — some schools shift these cut-offs or drop the plus/minus grades, so always check the syllabus for the scale that applies to you.
Students ask about this constantly: how many questions can you miss and still pass, or still get an A?
The chart answers it at a glance — on a 20-question test you can miss 8 and still pass at 60%, but only 1 and still hold an A−.
EZ Grader Charts for Common Test Sizes
10-Question Quiz Chart (exit tickets and quick quizzes)
| Wrong | Correct | Percentage | Letter grade |
|---|---|---|---|
| 0 | 10 | 100% | A+ |
| 1 | 9 | 90% | A− |
| 2 | 8 | 80% | B− |
| 3 | 7 | 70% | C− |
| 4 | 6 | 60% | D− |
| 5 | 5 | 50% | F |
| 6 | 4 | 40% | F |
| 7 | 3 | 30% | F |
| 8 | 2 | 20% | F |
| 9 | 1 | 10% | F |
| 10 | 0 | 0% | F |
Notice how brutal a 10-question quiz is: a single wrong answer drops a perfect paper to an A−, and two wrong answers land on a B−.
That is why short quizzes feel so unforgiving — and why a 9/10 quiz score is a genuinely good result, not a near-miss.
20-Question Test Chart (the classroom standard)
| Wrong | Correct | Percentage | Letter grade |
|---|---|---|---|
| 0 | 20 | 100% | A+ |
| 1 | 19 | 95% | A |
| 2 | 18 | 90% | A− |
| 3 | 17 | 85% | B |
| 4 | 16 | 80% | B− |
| 5 | 15 | 75% | C |
| 6 | 14 | 70% | C− |
| 7 | 13 | 65% | D |
| 8 | 12 | 60% | D− |
| 9 | 11 | 55% | F |
| 10 | 10 | 50% | F |
The 20-question chart is the one teachers reach for most, because each wrong answer is a clean 5% and the grade boundaries land on round numbers.
A student who misses 2 out of 20 scores 90% — an A− on this scale, though some schools with a straight 90+ scale would call it a plain A.
25-Question Test Chart
| Wrong | Correct | Percentage | Letter grade |
|---|---|---|---|
| 0 | 25 | 100% | A+ |
| 1 | 24 | 96% | A |
| 2 | 23 | 92% | A− |
| 3 | 22 | 88% | B+ |
| 4 | 21 | 84% | B |
| 5 | 20 | 80% | B− |
| 6 | 19 | 76% | C |
| 7 | 18 | 72% | C− |
| 8 | 17 | 68% | D+ |
| 9 | 16 | 64% | D |
| 10 | 15 | 60% | D− |
| 11 | 14 | 56% | F |
50-Question Test Chart (key rows)
On a 50-question test each wrong answer costs 2%, so the full chart runs to 51 rows. These are the rows teachers check most — the grade boundaries and the pass line:
| Wrong | Correct | Percentage | Letter grade |
|---|---|---|---|
| 0 | 50 | 100% | A+ |
| 1 | 49 | 98% | A+ |
| 2 | 48 | 96% | A |
| 3 | 47 | 94% | A |
| 5 | 45 | 90% | A− |
| 6 | 44 | 88% | B+ |
| 8 | 42 | 84% | B |
| 10 | 40 | 80% | B− |
| 12 | 38 | 76% | C |
| 15 | 35 | 70% | C− |
| 17 | 33 | 66% | D |
| 20 | 30 | 60% | D− |
| 21 | 29 | 58% | F |
For any other wrong count on a 50-question test, use the Test Grade Calculator — enter 50 and the number wrong, and it builds the full chart for you.
100-Question Exam Chart (key rows)
On a 100-question exam the percentage is simply the number correct, so the chart is the grade scale itself. The rows that matter:
| Wrong | Correct | Percentage | Letter grade |
|---|---|---|---|
| 0–3 | 100–97 | 100–97% | A+ |
| 4–7 | 96–93 | 96–93% | A |
| 8–10 | 92–90 | 92–90% | A− |
| 11–13 | 89–87 | 89–87% | B+ |
| 14–17 | 86–83 | 86–83% | B |
| 18–20 | 82–80 | 82–80% | B− |
| 21–23 | 79–77 | 79–77% | C+ |
| 24–27 | 76–73 | 76–73% | C |
| 28–30 | 72–70 | 72–70% | C− |
| 31–33 | 69–67 | 69–67% | D+ |
| 34–37 | 66–63 | 66–63% | D |
| 38–40 | 62–60 | 62–60% | D− |
| 41+ | 59 or fewer | 59% or below | F |
Worked Example: Grading 28 Quizzes in Under 10 Minutes
A teacher gives a 20-question quiz to a class of 28.
The old way — a calculator for every paper — takes roughly 20–30 seconds per paper, or about 10–14 minutes of pure arithmetic, plus the marking itself.
With an EZ grader chart, the teacher changes one habit: instead of grading one paper start to finish, she marks all 28 papers first, writing only the number wrong on each.
Then she sorts the stack by that number — all the “2 wrong” papers together, all the “5 wrong” papers together — and reads each group off the chart once.
Five groups, five lookups, and every paper in the stack is graded. The counting is still the work; the maths is gone.
The same batching trick works with the online tools: the Teacher Grader gives the percentage and letter for any total and wrong count in seconds.
And the Test Grade Calculator prints the full chart for the test size, so a teacher can keep it beside the stack instead of re-typing numbers.
In short, an EZ grader chart turns that batching trick into a routine.
Common Mistakes When Using an EZ Grader Chart
1. Using the wrong total. The most common error by far. A chart built for 20 questions gives wrong grades on a 25-question test — every row is off by a different amount, so the mistake is hard to spot afterwards.
Check the total before the first lookup, not after the tenth paper.
2. Counting right answers instead of wrong ones. On a long test it is tempting to count the correct answers and subtract.
That adds a subtraction step to every paper, and it is where tired graders slip. Count the wrong answers directly and look them up.
3. Forgetting half points and extra credit. A chart row only exists for whole numbers of wrong answers.
If a student earned half credit on a question, or the test carries extra-credit points, the chart answer is wrong — use a points-based calculation for that paper instead.
4. Rounding the wrong way at the boundary. The original chart rounded to the nearest whole percentage, giving the benefit of one-half.
But percentages like 86.67% (13 out of 15) are not rounded to 87% by every school — some leave them as they are, which keeps the grade a B rather than a B+.
If a student’s grade sits within a point of a boundary, check the school’s rounding rule before writing the letter down.
5. Applying the wrong scale. The chart gives a percentage; the letter comes from a scale, and scales differ.
A 90% is an A− on the plus/minus scale used on this site, but a plain A on a straight 90+ scale.
The chart never decides the letter by itself — the school’s scale does.
Chart, Calculator, or Both?
Use a printed chart when you are grading a stack of papers for one test size and want zero screen time — it is the fastest option for a single batch.
Use an online calculator when test sizes vary, when you need the full chart for an unusual size (like 37 questions), or when a paper has half points or extra credit.
Most teachers end up using both: the chart for the stack, the calculator for the exceptions.
If you grade often, bookmark the two tools on this site: the Teacher Grader for the quick one-paper lookup, and the Test Grade Calculator for the full chart of any test size.
And if you are a student wondering what your own score means, the miss-budget guide — how many questions you can miss and still pass — turns the same chart into a study plan.
Frequently Asked Questions
What is an EZ grader?
An EZ grader is a chart — originally a cardboard slide chart, now usually an online calculator — that converts the number of wrong answers on a test into a percentage score and letter grade, without doing division for each paper.
How do you use an EZ grader chart?
Match the chart to the total number of questions on the test, count how many answers are wrong, find that number in the chart’s left column, and read the percentage and letter grade across the row.
What does the original EZ grader look like?
The classic version is a cardboard sleeve with a sliding insert.
Sliding the insert until an arrow points to the test’s total number of problems lines the windows up with the right grades.
The front side covers tests of up to 50 problems and the reverse side up to 95.
Can I use an EZ grader chart for weighted or points-based tests?
No — the chart only works when every question is worth the same and marked right or wrong.
For points-based tests use the Class Grade Calculator, and for category-weighted courses use the Weighted Grade Calculator.
Why does one wrong answer hurt more on a short quiz?
Because each wrong answer costs 100 ÷ total questions percent. On a 10-question quiz that is 10% per mistake; on a 100-question exam it is just 1%.
Short tests are unforgiving by arithmetic, not by teacher choice.
Is 90% an A or an A−?
On the plus/minus scale used on this site, 90% is an A− (90–<93). On a straight scale without plus/minus grades, 90% is a plain A. Your school’s scale decides — always check the syllabus.
