Test Score to Grade: Convert Any Score to a Percentage and Letter Grade
Quick answer: Divide the points you earned by the points possible, then multiply by 100: (earned ÷ possible) × 100. A 17 out of 20 is 17 ÷ 20 × 100 = 85%, a B on the standard US scale. Then match the percentage to your school’s letter-grade cutoffs — typically A 90+, B 80–89, C 70–79, D 60–69, F below 60.
“What is 17/20 as a grade?” is one of the most searched questions in school life — and the answer takes four seconds once you know the method. This guide gives you the conversion formula, a 20-row reference table covering the most common test denominators (20, 25, and 50 points), the letter-grade scale, and — the part most conversion pages skip — what that quiz score actually does to your overall course grade.
The Conversion Formula
Percentage = (points earned ÷ points possible) × 100
That’s the entire method. Three examples to lock it in:
- 17/20: 17 ÷ 20 = 0.85 → × 100 = 85%
- 18/25: 18 ÷ 25 = 0.72 → × 100 = 72%
- 45/50: 45 ÷ 50 = 0.90 → × 100 = 90%
Then convert the percentage to a letter grade using your school’s scale. The standard US scale — the one most schools publish — is:
| Percentage range | Letter grade |
|---|---|
| 90–100% | A |
| 80–89% | B |
| 70–79% | C |
| 60–69% | D |
| Below 60 | F |
So 17/20 = 85% = B. 45/50 = 90% = A. 18/25 = 72% = C. Always confirm your school’s cutoffs — some schools start A at 93, and plus/minus scales add finer bands — but the conversion math never changes.
Common Test Scores Converted: Reference Table
The table below covers the fractions students look up most often. Every value is computed from the formula above — bookmark this section for quiz night.
| Score | Percentage | Letter grade |
|---|---|---|
| 20/20 | 100% | A |
| 19/20 | 95% | A |
| 18/20 | 90% | A |
| 17/20 | 85% | B |
| 16/20 | 80% | B |
| 15/20 | 75% | C |
| 14/20 | 70% | C |
| 13/20 | 65% | D |
| 12/20 | 60% | D |
| 11/20 | 55% | F |
| 25/25 | 100% | A |
| 23/25 | 92% | A |
| 21/25 | 84% | B |
| 18/25 | 72% | C |
| 15/25 | 60% | D |
| 45/50 | 90% | A |
| 40/50 | 80% | B |
| 35/50 | 70% | C |
| 30/50 | 60% | D |
| 25/50 | 50% | F |
A score not on the list? Use the formula — or skip the math entirely with Calcrio’s free grade calculator, which converts any score and shows what it does to your course grade.
Converting Odd Denominators (37 Points, 63 Points, 150 Points…)
Not every test comes out of 20, 25, or 50. The method is identical — only the division is messier, so here’s one worked example to prove it:
Example: 29 out of 37. 29 ÷ 37 = 0.7838 → × 100 = 78.38% ≈ 78%, a C on the standard scale. And 121 out of 150: 121 ÷ 150 = 0.8067 → × 100 = 80.67% ≈ 81%, a B.
Two tips for ugly denominators. First, round only at the end: keep two decimals through the multiplication, then round the final percent. Rounding 29/37 to 0.78 early gives 78% anyway here, but on borderline scores (89.5 vs 90) early rounding can flip a letter. Second, if your teacher drops the lowest-scoring question after grading, convert using the adjusted total, not the printed one — a dropped 5-point question turns 29/37 into 29/32 = 90.6%, an A.
The Plus/Minus Scale: Finer Bands
Many schools split each letter into three bands. If yours does, use this table instead of the flat scale above:
| Percentage | Grade | Percentage | Grade |
|---|---|---|---|
| 97–100 | A+ | 77–79 | C+ |
| 93–96 | A | 73–76 | C |
| 90–92 | A− | 70–72 | C− |
| 87–89 | B+ | 67–69 | D+ |
| 83–86 | B | 63–66 | D |
| 80–82 | B− | 60–62 | D− |
Below 60 is an F. On this scale, 17/20 = 85% lands as a B, while 18/20 = 90% is an A− rather than a flat A. The percentage you computed doesn’t change — only which row it falls in. When a syllabus says “A− or better required,” this table is the one that decides.
What Your Quiz Score Does to Your Course Grade
Here is the question conversion pages never answer: you got 17/20 (85%) — so what? What does that do to your actual grade? The answer depends on the quiz’s weight in your course.
Worked example: quizzes are worth 15% of your course grade. You scored 17/20 = 85%.
- Convert the score: 17 ÷ 20 × 100 = 85%
- Multiply by the quiz category’s weight: 85 × 0.15 = 12.75 course points
- A perfect 20/20 would have earned 100 × 0.15 = 15.0 course points
- The three missed quiz points cost you 15.0 − 12.75 = 2.25 points off your final course grade
That’s the real meaning of a quiz score: 17/20 isn’t just “a B on a quiz” — it’s 2.25 points of your final grade. And notice the leverage: on a 20-point quiz worth 15% of the course, each missed quiz point costs about 0.75 points of course grade (15 ÷ 20). A 3-point quiz mistake hurts three times less than a 3-point mistake on a 60-point test worth the same 15%.
This is the bridge from score conversion to weighted grading — and it’s exactly what our weighted grade guide covers step by step. Once a score is converted to a percent, it flows into the category average, which flows into the course grade. One pipeline, end to end.
Why the Same Score Can Be a Different Grade
Two caveats that confuse students every year:
Plus/minus scales. Some schools split each band: 90–92 might be an A−, 93–96 an A, 97–100 an A+. On such a scale, 18/20 = 90% is an A−, not a flat A. The percentage is identical everywhere; the letter depends on the school’s published bands.
Curved or scaled grading. Some instructors curve tests — adding points, dropping questions, or grading on a distribution. If your teacher adds 5 points to every score, your 17/20 becomes 22/25 = 88%. Conversion math still works; you just convert the adjusted score. When in doubt, ask what the curve did before converting.
FAQ
What is 17/20 as a grade?
17 ÷ 20 × 100 = 85%, which is a B on the standard US scale (80–89). On a plus/minus scale, 85% is typically a B as well (B− usually starts around 80–82).
Is 85% a B everywhere?
In the US, almost always — 85% sits squarely in the standard B band (80–89). But schools set their own cutoffs, so confirm your syllabus. Internationally, grading works differently: in France’s 20-point system, 17/20 is “excellent” (roughly top 5%), because the scale runs 0–20 rather than 0–100%.
How do I convert a score when the test has extra credit?
Convert using the adjusted total. If a 20-point test had 2 points of extra credit available and you earned 21: 21 ÷ 20 × 100 = 105%. Yes, over 100% is fine here — it just means you earned bonus points. Some teachers cap at 100%; check the policy.
What is 18/25 as a grade?
18 ÷ 25 × 100 = 72%, a C on the standard scale. If that was a quiz worth 15% of your course, it contributed 72 × 0.15 = 10.8 of 15 possible course points.
Why do I need the letter grade at all?
Letters are how transcripts, GPA, and academic standing work — but the percentage is the working number for all grade math. Always do calculations (weighted averages, final-exam planning) in percentages, then convert to a letter at the very end. Our guide on what you need on your final to get an A shows why: the formula needs your numeric current grade.
Can I convert GPA-style grades back to percentages?
Roughly, but not exactly — GPA bands are coarse (a 3.0 could be anywhere from 80 to 89 depending on the school). Percentages carry more information than letters, which is why you should keep your gradebook in percent form until the final conversion.
Conclusion
Converting a test score is a four-second calculation — earned divided by possible, times 100 — but it’s the first link in a chain: the percentage feeds your category average, the category average feeds your weighted course grade, and the course grade decides what you need on the final. Get the conversion right and everything downstream is trustworthy.
Stop converting by hand: the free Calcrio Grade Calculator turns any score into a percentage, a letter grade, and its impact on your course — all from one screen.