About the Test Score Calculator
When a test comes back marked, the first thing most students want to know is the percentage and the letter grade. Teachers need the same figures for every paper they mark, often dozens at a time. The calculation is simple — the number right divided by the total — but doing it repeatedly by hand is slow and easy to get wrong, especially with awkward totals such as 23 or 37 questions.
This test score calculator turns the number of questions wrong or right into a percentage and a letter grade. It shows how much each question is worth, and it lists the most questions you can miss and still earn an A, B, C or D, so it works as an instant grading chart for any length of test. It works just as well with points: enter the total points and the points lost or earned.
How to Use the Test Score Calculator
Choose Number wrong or Number correct.
Enter the total questions or points on the test.
Enter the number wrong or correct.
Read the percentage, letter grade and the table of how many you can miss for each grade.
The Formula
correct = total − wrong
score = correct ÷ total × 100
each question is worth 100 ÷ total percent
most you can miss for a grade = ⌊ total × (1 − cut-off ÷ 100) ⌋Step-by-Step Examples
7 wrong out of 50.
correct 50 − 7 = 43
score 43 ÷ 50 × 100 = 86% → a B
each question is worth 2%For an A at 93% you need 46.5 correct, so you can miss at most 3 questions. For a B you can miss 8, for a C 13 and for a D 17.
17 correct out of 20: 17 ÷ 20 × 100 = 85%, a B. Each question is worth 5%.
29 out of 30: 29 ÷ 30 × 100 = 96.67%, an A.
Points: losing 12 points on an 80-point test gives 68 ÷ 80 = 85%.
How Test Length Changes Each Mistake
On a short test each question carries a lot of weight. With 10 questions, one mistake costs 10 percentage points and can drop you a whole letter grade; with 100 questions, one mistake costs just one point. That is why a single slip on a short quiz can feel so costly, and why longer tests usually give a more reliable picture of what a student knows. When you plan your study, remember that on a short quiz, careful checking of each answer is worth as much as learning new material.
Grading Charts and EZ Graders
For decades teachers have used printed grading charts and sliding cardboard "EZ graders" to read off a percentage from the number of questions and the number wrong. This calculator does the same job for any number of questions and adds the letter grade. The "most you can miss" line is the chart in reverse: it tells you, before or after a test, how many mistakes each grade allows. Teachers marking a stack of papers can keep the total fixed and simply change the number wrong for each student.
Partial Credit and Different Point Values
Many tests do not give every question the same value. A test might have 20 one-point multiple-choice questions and four 5-point written answers, or award partial credit. In that case, work in points rather than questions: enter the total points available and the points earned or lost. The percentage is the same calculation. If there are bonus questions, add their points only to the score, not the total, and the percentage can exceed 100%.
Letter Grade Bands
The calculator uses the common US plus/minus bands: 93% or more is an A, 90% an A-, 87% a B+, 83% a B, and so on down to 65% for a D, with anything lower an F. The "most you can miss" line uses the lowest cut-off for each whole letter: 93% for an A, 83% for a B, 73% for a C and 65% for a D. Many schools use a simpler ten-point scale, where an A starts at 90% and a D at 60%; for those, the letter grade converter shows both scales.
Tracking Scores Over Time
A single test score says little on its own. Recording each result with its percentage lets you spot trends — steady improvement, a weak topic that keeps costing marks, or careless errors on long papers. Feed the percentages into the grade calculator with their weights to see your running course grade.
Negative Marking
Some multiple-choice exams deduct marks for wrong answers to discourage guessing. For those, subtract the penalty from the number correct first, then enter the adjusted score as points earned against the total points available.
Understanding Your Result
The headline is your percentage and letter grade.
The right and wrong line shows the numbers correct and wrong.
The each question line shows how many percentage points each question or point is worth.
The most you can miss line lists the maximum mistakes for an A, B, C and D.
When Should You Use This Calculator?
Use it to work out your score as soon as a test comes back.
Use it as a teacher to grade a stack of papers quickly.
Use it before a test to see how many mistakes each grade allows.
Common Mistakes
Dividing by the number wrong. Divide the number correct by the total.
Mixing questions and points. Use one or the other throughout.
Adding bonus points to the total. Bonus points belong only in the score.
Assuming everyone uses the same bands. Check your teacher's grading scale.