Set the number of questions and get the whole chart — every points-wrong value against its percentage and letter grade. Prints on one page.
Percentage
a B — 4 wrong out of 25
Letter gradeB
Correct21
Each question4%
Points wrong to percentage, out of 25
Wrong
Correct
Score
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
12
13
52%
F
13
12
48%
F
14
11
44%
F
15
10
40%
F
16
9
36%
F
17
8
32%
F
18
7
28%
F
19
6
24%
F
20
5
20%
F
21
4
16%
F
22
3
12%
F
23
2
8%
F
24
1
4%
F
25
0
0%
F
Letters use the standard US bands (A 93–96, A− 90–92, and so on). If your school uses different cut-offs, the percentage column is the part that transfers.
This calculator needs JavaScript to recalculate. The answer shown above was worked out when the page was built and is correct for the date in the address bar.
When you are working through a stack of papers, you count the marks you made — not the ones you did not. Counting errors is faster than counting correct answers and it is far less error-prone, because you are counting a small number rather than a large one. On a 25-question test you count to four, not to twenty-one.
The physical E-Z Grader slide chart has been on teachers' desks for decades for exactly this reason. This page is the same idea: set the test length once, and the chart tells you the percentage for every possible number of errors. Look up, write the grade, move to the next paper.
Using the chart
Set the number of questions and the full chart appears — every points-wrong value from zero to the total, with its percentage and letter grade. It prints on one page and is designed to be printed; a laminated chart on a desk beats a phone with a screen lock every time.
The single-score lookup below it is for the odd paper that does not fit — partial credit, a skipped question, a test of unusual length.
Worked example
A 25-question test with four wrong: 21 ÷ 25 = 84%, a B.
Each question on a 25-mark test is worth exactly 4 percentage points, which makes the chart unusually easy to read: every error costs one clean step, and the letter boundaries fall at predictable places. Three wrong is 88% and a B+, two wrong is 92% and an A−. Compare a 30-question test, where each question is worth 3.33 points and the boundaries land mid-question — that is where a chart earns its place over mental arithmetic.
The formula
percentage = (total − wrong) ÷ total × 100
Rounded half-up to one decimal place. Letter bands follow the common US convention set out on the letter grade to GPA page; if your school's bands differ, the percentage column is the one to work from.
Where this stops being reliable
The chart assumes every question is worth the same. As soon as a test has a 10-point essay alongside 1-point multiple choice, points-wrong stops being meaningful and you have to work in points — the test grade calculator handles that. Partial credit has the same problem: half a mark wrong is not a chart row. And on very short tests the chart gets coarse — on a 10-question test every error costs 10 percentage points and there is no meaningful distinction between a B+ and a B.
Common questions
How do I use an easy grader?
Set the number of questions on the test, then find the row matching how many the student got wrong. The chart gives the percentage and the letter grade. Counting errors rather than correct answers is faster and more reliable when you are working through a stack.
What percentage is 4 wrong out of 25?
84%, a B on a standard scale. On a 25-question test each question is worth exactly 4 percentage points, so every additional error drops the grade by 4.
How do I grade a test with an unusual number of questions?
Enter the total above and the chart regenerates for that length — 17 questions, 43 questions, whatever the test actually has. There is no fixed set of lengths.
How do I handle partial credit on a chart?
You cannot, cleanly — a chart has whole rows. Use the single-score lookup instead and enter the decimal, or switch to the test grade calculator, which takes any score against any total.
Can I print the chart?
Yes. It is laid out to fit one page and prints without the site furniture around it. A printed chart on the desk is faster than any screen when you are marking.
What if my questions are worth different points?
Then points-wrong does not describe the score and the chart will mislead you. Work in points earned out of points possible using the test grade calculator — two wrong answers worth five marks each is a very different result from two worth one mark each.