Hong Life CalculatorsUnderstanding the test grade calculator — concept and principle
This calculator turns the number of questions and the number you got wrong into a percentage score and a letter grade. It also shows what each question is worth and how many you can miss and still get an A, B or C. Teachers use it for quick marking; students use it to check a result or set a target.
How it is calculated
Score (%) = (total − wrong) ÷ total × 100
Value of one question = 100 ÷ total percentage points
Most wrong answers for a grade = total × (1 − cut-off), rounded down
- Letter grade on the common US scale: A 90–100, B 80–89, C 70–79, D 65–69, F below 65, applied to the unrounded percentage.
- If questions carry different points, enter total points and points lost instead.
The principle
A percentage is a share out of 100. When every question has the same weight, each one carries an equal slice of the score, so missing one always costs 100 ÷ total points. The grade limits work the other way round: to stay at or above 90 %, the wrong answers can be at most 10 % of the total. Because you cannot miss part of a question, that number is rounded down. Short tests are coarse: on a 10-question quiz each mistake costs 10 points, while on a 100-question test it costs 1.
Worked example
Default inputs: 40 questions, 6 wrong, US scale.
- Correct answers = 40 − 6 = 34.
- Score = 34 ÷ 40 × 100 = 85 %, which is a B (80–89).
- Each question is worth 100 ÷ 40 = 2.5 points.
- Most wrong for an A = 40 × 0.1 = 4; for a B = 40 × 0.2 = 8; for a C = 40 × 0.3 = 12.
| Number of questions (or total points) | Score (%) |
|---|---|
| 10 | 40% |
| 20 | 70% |
| 30 | 80% |
| 40 | 85% |
| 50 | 88% |
| 60 | 90% |
| 80 | 92.5% |
How to read the result
The percentage is the dependable number; the letter depends on which scale your school uses. Many schools use 90/80/70/60, some add plus and minus grades, and Korean schools often report achievement levels or ranks instead. Check your syllabus. Use the "most wrong" lines as a target: on this 40-question test, two more mistakes would still be a B, but three more would drop the score to 77.5 %, a C.
Common mistakes
- Entering correct answers in the "wrong" box.
- Using question counts when questions have different point values.
- Assuming the letter scale here is the one your school uses.
- Rounding the percentage up before choosing the grade, such as calling 89.5 % an A.
Frequently asked questions
What percentage is 34 out of 40?
85 %.
Is 85 % an A or a B?
On the common US scale it is a B. Under a scale with an A starting at 85 it would be an A.
How many can I miss on a 25-question test to get 80 %?
Five, because 25 × 0.2 = 5, which leaves 20 correct = 80 %.
Sources: College Board, BigFuture, "How to Convert Your GPA to a 4.0 Scale" (letter-grade bands)