Grade Calculator (EZ Grader)
This grading calculator works like an EZ grader: enter how many questions or points a test has and how many were wrong, and it gives the score, the percentage and the letter grade. With 3 wrong out of 20, that is 17/20 = 85%, a B. Below the result, an EZ grader chart lists every possible number wrong with its percentage and letter, so you can grade a whole stack of papers from one table.
How to use the grade calculator
- Enter the number of questions or total points on the test. The default is 20.
- Enter the number wrong. The default is 3. If you would rather count what was right, use the toggle to switch to number correct.
- Choose a letter scale: the standard A/B/C/D/F scale with cutoffs at 90, 80, 70 and 60, or the plus/minus scale.
- Read the score, percentage and letter at the top. With the defaults it shows 17/20 = 85%, B.
The chart underneath is the EZ grader. It lists every possible number wrong, from 0 up to the total (for tests of up to 200 questions or points), with the percentage and letter grade for each row. The row that matches your current entry is highlighted. For a teacher, that means you set the test length once and then read each student’s grade straight off the chart as you mark.
How the grading calculator works out a percentage
A test grade is a fraction turned into a percentage. The number correct goes on top, the number possible goes underneath, and multiplying by 100 puts it on a 0–100 scale. For the default test:
This is the same calculation as turning any “X out of Y” into a percentage, which the X out of Y as a percentage guide covers with a full conversion table. For a single score with no grade attached, the what percent of calculator does the division the same way.
What each wrong answer costs
On a test where every question is worth the same, each wrong answer takes off the same slice: 100 ÷ total percentage points. This is why an EZ grader chart drops by a fixed step on each row.
| Questions | Each wrong answer costs | Most wrong for an A (90%) | For a B (80%) | For a C (70%) | For a D (60%) |
|---|---|---|---|---|---|
| 10 | 10 points | 1 | 2 | 3 | 4 |
| 15 | ≈ 6.67 points | 1 | 3 | 4 | 6 |
| 20 | 5 points | 2 | 4 | 6 | 8 |
| 25 | 4 points | 2 | 5 | 7 | 10 |
| 30 | ≈ 3.33 points | 3 | 6 | 9 | 12 |
| 40 | 2.5 points | 4 | 8 | 12 | 16 |
| 50 | 2 points | 5 | 10 | 15 | 20 |
| 100 | 1 point | 10 | 20 | 30 | 40 |
EZ grader chart for a 20-question test
This is what the chart below the calculator shows with the default 20 questions on the standard scale. Rows past 9 wrong are all F and drop by 5 points each.
| Number wrong | Score | Percentage | Letter |
|---|---|---|---|
| 0 | 20/20 | 100% | A |
| 1 | 19/20 | 95% | A |
| 2 | 18/20 | 90% | A |
| 3 | 17/20 | 85% | B |
| 4 | 16/20 | 80% | B |
| 5 | 15/20 | 75% | C |
| 6 | 14/20 | 70% | C |
| 7 | 13/20 | 65% | D |
| 8 | 12/20 | 60% | D |
| 9 | 11/20 | 55% | F |
| 10 | 10/20 | 50% | F |
An EZ grader is the name teachers use for this kind of chart, after the sliding cardboard charts that show every score for a test length at once. The calculator version does the same job for any total, including awkward ones like 23 or 37 questions where the percentages do not come out in round numbers.
Here is the top of the chart for a 25-question test, where each wrong answer costs 4 points:
Worked examples
Example: 30 questions, 8 wrong
A 30-question quiz where the student missed 8.
The percentage does not come out even, so it is rounded to two decimal places. The letter does not depend on the rounding here, but near a cutoff it can; see the next section.
Example: a 50-point test with 7 points lost
Questions are worth different amounts, so grade by points.
Enter 50 as the total and 7 as the number wrong. The calculator does not care whether the units are questions or points, only that the wrong count uses the same units as the total.
Example: counting correct answers instead
A 15-question quiz with 13 right.
Switch the toggle to number correct and enter 13. One more right answer would make it 14/15 ≈ 93.33%, an A.
Letter grade scales: standard and plus/minus
The standard US scale gives an A for 90–100, B for 80–89, C for 70–79, D for 60–69 and F below 60. Scales vary by school, district and teacher, so check the syllabus before relying on any letter.
The plus/minus option splits each band. A widely used version looks like this:
| Letter | Percentage | Letter | Percentage |
|---|---|---|---|
| A+ | 97–100 | C+ | 77–79 |
| A | 93–96 | C | 73–76 |
| A− | 90–92 | C− | 70–72 |
| B+ | 87–89 | D+ | 67–69 |
| B | 83–86 | D | 63–66 |
| B− | 80–82 | D− | 60–62 |
Under that scale the default 85% is still a B, while 88% would be a B+ and 92% an A−.
Scores between the cutoffs
Percentages like 89.5% or 79.6% fall in the gap between the whole-number bands. Whether 89.5% counts as an A depends on the school’s rounding policy: some round to the nearest whole percent first, others require the full 90.00%. The rounding calculator shows what a score becomes under each rounding rule, which helps when writing or applying that policy.
From one test to a course grade
The grade calculator handles one test or assignment at a time. A course grade usually combines several, often with different weights: tests might count for 50% of the grade and homework for 20%. Averaging the test percentages is a job for the average calculator when every test counts the same, and for the weighted average calculator when they do not.
The guide to calculating your final grade walks through a full semester with weighted categories. If the final exam is still to come, the final grade calculator works out the score you need on it to reach a target grade.
Bonus questions, partial credit and curves
A few grading situations need a small adjustment to the basic fraction.
- Bonus questions. Keep the total at the number of regular questions and count bonus answers as extra correct. A student who gets 21 right on a 20-question test with 2 bonus questions scores
21 ÷ 20 × 100 = 105%. The chart stops at 0 wrong, so work bonus scores out by hand or with the percentage calculator. - Partial credit. Grade in points rather than questions, and allow half points in the number wrong.
- Adding points to everyone. If the highest score was 88% and the teacher adds 12 points to every paper, a 70% becomes 82%. Every row of the chart shifts up by the same amount.
- Scaling to the top score. Another common curve multiplies each score by
100 ÷ top score. With a top score of 88%, a 70% becomes70 × 100 ÷ 88 ≈ 79.55%. Lower scores rise by less than higher ones under this method.
Which curve, if any, is used is a teacher’s or school’s decision; the calculator always reports the raw, uncurved percentage.
Common mistakes
- Dividing the number wrong by the total. 3 ÷ 20 = 15% is the share you got wrong. The grade is the share right: 85%.
- Mixing questions and points. If questions carry different points, count points lost, not questions missed.
- Assuming each wrong answer costs a round number. On a 30-question test each one costs about 3.33 points, not 3.
- Averaging raw scores from tests of different lengths. 9/10 and 30/50 average to 75% as percentages but 39/60 = 65% as points. Decide which your class uses.
- Applying the wrong letter scale. The 90/80/70/60 cutoffs are common but not universal.
Frequently asked questions
How do you use an EZ grader?
Find the column or row for the number of questions on the test, then read across from the number wrong to the percentage. On this page, enter the total once and the chart below the calculator lists every number wrong with its percentage and letter. For a 20-question test, 3 wrong reads as 85%, a B.
What grade is 17 out of 20?
17 out of 20 is 85%, which is a B on the standard 90/80/70/60 scale. Divide 17 by 20 to get 0.85 and multiply by 100. Each question on a 20-question test is worth 5 percentage points, so 3 wrong answers take 15 points off 100.
How many can you miss on a 25-question test and still get an A?
Two. With 2 wrong the score is 23/25 = 92%, an A. With 3 wrong it is 22/25 = 88%, a B. Each question on a 25-question test is worth 4 percentage points, so the A band from 90 to 100 has room for only two misses.
What is 22 out of 30 as a grade?
22 out of 30 is about 73.33%, which is a C on the standard scale. Divide 22 by 30 to get 0.7333 and multiply by 100. On a common plus/minus scale it would be a C, since 73.33% sits in the 73–76 band.
How does a grading calculator work?
A grading calculator subtracts the number wrong from the total to get the number correct, divides by the total and multiplies by 100. It then looks the percentage up on a letter scale. For 43 points out of 50, 43 ÷ 50 × 100 = 86%, which is a B on the standard scale.
Is 89.5% an A or a B?
It depends on the school. On a strict 90% cutoff, 89.5% is a B. If the school rounds to the nearest whole percent first, it becomes 90% and an A. Because policies differ, check the course syllabus or ask the teacher which rule applies.
Can I use the grade calculator for points instead of questions?
Yes. Enter the total points as the number of questions and the points lost as the number wrong. A 40-point test with 4.5 points off gives 35.5 ÷ 40 × 100 = 88.75%, a B. The calculation is identical; only the units change.
Related calculators
Guides that use this calculator
Longer explanations of the method behind it, with worked examples.
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