How the easy grader finds the percent
The easy grader uses one short formula. It takes the number of questions on the test and subtracts the number wrong. That gives the number correct. Then it divides the number correct by the total questions and multiplies by 100.
Here is the formula in plain text: percent = (questions - wrong) / questions x 100.
Say a quiz has 20 questions and you mark 3 wrong. The number correct is 20 minus 3, which is 17. Then 17 divided by 20 is 0.85. Multiply by 100 and the percent is 85. On the scale this site uses, 85 percent is a B.
This is the same maths a paper EZ grader wheel does. The difference is that a wheel only shows one row at a time. This page can show the whole chart for the test length you enter.
Rounding and the letter grade
The percent shows one decimal place. So 17 out of 20 shows as 85.0 percent. A score like 16 out of 19 shows as 84.2 percent.
The letter grade uses the unrounded value. That matters near a cutoff. Suppose a score works out to 89.96 percent. Rounded to one decimal, it looks like 90.0. But the unrounded value is below 90, so the letter is B+. The tool checks the real number first, then rounds only for display.
This site uses one letter scale on every calculator. It is the most common scale in US schools:
| Letter | Percent |
|---|---|
| A+ | 97-100 |
| A | 93-96 |
| A- | 90-92 |
| B+ | 87-89 |
| B | 83-86 |
| B- | 80-82 |
| C+ | 77-79 |
| C | 73-76 |
| C- | 70-72 |
| D+ | 67-69 |
| D | 63-66 |
| D- | 60-62 |
| F | below 60 |
Schools differ. Your district may use a 90 for an A, or a 7 point scale, or plus and minus cutoffs in other places. Check your own grading policy before you hand back a score.
Using a custom letter scale
You can set your own cutoffs if your school does not match the table. Enter the lowest percent for each letter. For example, if your school gives an A at 92, set the A cutoff to 92. If it gives no A+, turn that row off.
Keep two things in mind when you build a custom scale. First, the cutoffs must not overlap. Second, they must cover every score from 0 to 100. A gap means some scores have no letter.
Once your scale is set, the chart below the tool updates to match it. That way the printed chart and the letter on screen agree.
The full chart for one test length
The chart lists every number wrong from 0 up to the total questions. Each row shows the number correct, the percent, and the letter. For a 20 question quiz, the chart has 21 rows.
Teachers print this chart and keep it on a desk. When you grade a stack of papers, you find the row for the number wrong and read across. No long division for each paper.
Here is a short sample for a 20 question test:
| Wrong | Correct | Percent | Letter |
|---|---|---|---|
| 0 | 20 | 100.0 | A+ |
| 1 | 19 | 95.0 | A |
| 2 | 18 | 90.0 | A- |
| 3 | 17 | 85.0 | B |
| 4 | 16 | 80.0 | B- |
| 5 | 15 | 75.0 | C |
| 6 | 14 | 70.0 | C- |
| 7 | 13 | 65.0 | D |
| 8 | 12 | 60.0 | D- |
| 9 | 11 | 55.0 | F |
The full chart covers all rows, including these ten.
What this tool does not do
This tool does not grade on a curve. A curve changes the score after the fact. It might add points to every paper, or set the top score as the new 100, or drop the lowest question. Those choices depend on the class and the test. This page only converts a raw score to a percent and a letter.
If you want to curve, decide the rule first, then apply it to the raw scores. After that, you can run the curved scores through the same formula.
For weighted categories, a final exam target, or GPA, use the other pages on the site. The weighted grade calculator handles categories with different weights. The final grade calculator tells you what you need on the final. The GPA calculator turns letter grades and credits into a grade point average. Every formula is listed at how we calculate.