How to Convert Any Test Score to a Letter Grade
A test score becomes a letter grade in one step: divide the points you earned by the points possible, multiply by 100, then match that percentage to your school’s scale. Everything else — the table, the boundary cases, the rounding question — is detail around that single division.
This guide uses the standard United States plus/minus scale, the same one behind every calculator on this site: A+ from 97, A from 93, A- from 90, B+ from 87, B from 83, B- from 80, C+ from 77, C from 73, C- from 70, D+ from 67, D from 63, D- from 60, and F below 60.
The formula behind the letter
Percentage is earned points divided by possible points, times 100.
Percentage = (Points earned ÷ Points possible) × 100
A 43 out of 50 quiz is 43 ÷ 50 = 0.86, which is 86%. On the plus/minus scale, 86% sits at the top of the B band (83 to 86.99), so the letter is B. If you would rather type the numbers than do the division, the grade calculator and the percentage calculator both return the percentage and the letter at once.
The letter is not a second calculation. It is a lookup: find the highest band whose minimum is at or below your percentage.
Worked example: 43 out of 50
Start with the raw score. 43 correct out of 50 questions is 86%.
Two points would change the outcome. 45 out of 50 is 90%, and 90 is the first A- score on this scale. That is the part students underestimate: on a 50-question test, one question is worth 2 percentage points, so a single lucky correction can move a B to an A-.
The same logic runs the other way. 42 out of 50 is 84%, still a B, but 41 out of 50 is 82%, which drops to a B-. A two-point swing crosses a letter boundary in both directions.
Common scores and their letters
These are the conversions people look up most often. Each one uses the plus/minus scale above, and the full chart covers more than 350 score combinations on the score to grade page.
| Score | Percentage | Letter | Grade points |
|---|---|---|---|
| 44 out of 50 | 88.00% | B+ | 3.3 |
| 43 out of 50 | 86.00% | B | 3.0 |
| 34 out of 40 | 85.00% | B | 3.0 |
| 15 out of 18 | 83.33% | B | 3.0 |
| 18 out of 23 | 78.26% | C+ | 2.3 |
| 12 out of 18 | 66.67% | D | 1.0 |
| 15 out of 25 | 60.00% | D- | 0.7 |
| 18 out of 20 | 90.00% | A- | 3.7 |
A 12 out of 18 is the awkward one. 66.67% looks close to 67, but 67 is the D+ cutoff, so the exact score lands one step lower at D.
Where one point changes the letter
Letter grades flip at fixed percentages, and the flip is unforgiving: 86.9% is a B, while 87% is a B+.
| Exact percentage | Letter |
|---|---|
| 59.9% | F |
| 60.0% | D- |
| 66.9% | D |
| 67.0% | D+ |
| 82.9% | B- |
| 83.0% | B |
| 86.9% | B |
| 87.0% | B+ |
| 89.9% | B+ |
| 90.0% | A- |
How many questions that gap represents depends on the test length. One question on a 20-question test is 5 percentage points, enough to jump two letter steps. One question on a 100-question test is a single point, which rarely changes anything.
That is also why the same letter can feel easier to earn in one class than another. A 90% on a 10-question quiz allows one wrong answer. A 90% on a 50-question test allows five.
Rounding: where the number and the letter disagree
Teachers differ on one detail that decides close calls: whether they round the percentage before or after they apply the letter cutoff.
If a test works out to 86.995%, the display rounds to 87.00%, but the exact value is still below 87. A teacher who rounds the percentage first records a B+. A teacher who applies the cutoff to the exact value records a B. The calculators here match the exact percentage first and only round the display, so the letter always reflects the real score.
If a grade matters — a scholarship threshold, an honour roll cut line — ask which order your teacher uses. It is a one-sentence question that resolves a surprising number of disputes.
When points are only part of the grade
A single test usually does not decide a course. Most syllabi weight categories, for example tests 50%, quizzes 20%, homework 20% and the final exam 10%. In that structure, a 43 out of 50 becomes 43 points inside the test category, and the course percentage is the sum of each category score times its weight.
That is a different calculation from the one on this page, and the weighted grade calculator handles it. The conversion from percentage to letter stays exactly the same once the course percentage exists.
If your class is graded purely on total points — 480 out of 600 across the term, no category weights — the points grade calculator is the closer match.
Frequently asked questions
What is 43 out of 50 as a grade?
43 divided by 50 is 0.86, or 86%. That is a B on the standard plus/minus scale, worth 3.0 grade points.
What is 15 out of 18 as a grade?
15 divided by 18 is 0.8333, or 83.33%. That is a B, just above the 83 cutoff, worth 3.0 grade points.
Is 89% an A?
Not on the plus/minus scale, where A- starts at 90 and B+ covers 87 to 89.99. On a scale without plus or minus grades, where A starts at 90 and B starts at 80, an 89% is a B as well.
Does a curve change the conversion?
A curve changes the points before the conversion. If a teacher adds 5 points to every paper, recalculate the percentage with the new earned points, then match that percentage to the scale. The letter table itself does not move.
Why does 66.67% show as a D and not a D+?
D+ starts at 67.0%, so 66.67% is below the cutoff even though it displays close to 67. Percentages are compared at full precision, not at the rounded value shown on screen.
Related reading
If you are converting a whole course rather than a single test, the letter grade and GPA guide explains how percentages become grade points and then how those points average into a GPA. For the arithmetic of a single test with missed questions, the test grade guide walks through the same division with different numbers.