What Grade Is 18/20? It’s 90% — an A− (and When It Isn’t)
The short answer: 18/20 is 90%, which is an A− on a plus/minus grading scale — and a plain A on a straight 90/80/70/60 scale with no plus or minus. That split is exactly why this score gets searched so often: 90% sits precisely on a boundary, so the same paper is an A− in one classroom and an A in the next. This guide gives you the full answer — the calculation, the complete /20 score table, what 18/20 means for your GPA, and why your teacher might see it differently from your friend’s teacher.
Try it yourself: our test grade calculator works out any score out of 20 (or any test size) in one click, with the full wrong-answer chart. For any percentage at all, use our letter grade calculator.
How to Calculate 18 Out of 20
The calculation is the same one that works for every fraction:
Percentage = correct answers ÷ total questions × 100
So: 18 ÷ 20 × 100 = 0.9 × 100 = 90%.
Then the percentage meets the scale. On the standard plus/minus scale used across this site, the bands are A+ 97–100, A 93–<97, A− 90–<93, B+ 87–<90, B 83–<87, and so on down to F below 60. 90% is the very first number inside the A− band — the lowest score that still counts as an A-range grade. One question less (17/20 = 85%) and you are a B; one question more (19/20 = 95%) and you are a plain A.
On a school that does not use plus/minus grades, the scale is simpler: A is 90–100, B is 80–89, C is 70–79, D is 60–69, F is below 60. On that scale, 90% is a plain A — the same paper, the same 18 correct answers, a different letter on the report card. Neither school is wrong; they just draw the lines differently. The rest of this guide uses the plus/minus scale unless it says otherwise, because that is the scale most US schools use — but it flags the straight-scale answer every time it matters.
The Complete /20 Score Table
Every possible score out of 20, with the percentage, the letter grade on the plus/minus scale, and the GPA points it is worth. Bookmark this page and you will never need to calculate a /20 score again.
| Score | Percentage | Letter Grade | GPA Points |
|---|---|---|---|
| 20/20 | 100% | A+ | 4.0 |
| 19/20 | 95% | A | 4.0 |
| 18/20 | 90% | A− | 3.7 |
| 17/20 | 85% | B | 3.0 |
| 16/20 | 80% | B− | 2.7 |
| 15/20 | 75% | C | 2.0 |
| 14/20 | 70% | C− | 1.7 |
| 13/20 | 65% | D | 1.0 |
| 12/20 | 60% | D− | 0.7 |
| 11/20 | 55% | F | 0.0 |
| 10/20 | 50% | F | 0.0 |
| 9/20 | 45% | F | 0.0 |
| 8/20 | 40% | F | 0.0 |
| 7/20 | 35% | F | 0.0 |
| 6/20 | 30% | F | 0.0 |
| 5/20 | 25% | F | 0.0 |
| 4/20 | 20% | F | 0.0 |
| 3/20 | 15% | F | 0.0 |
| 2/20 | 10% | F | 0.0 |
| 1/20 | 5% | F | 0.0 |
| 0/20 | 0% | F | 0.0 |
Three things jump out of this table. First, every question on a 20-question test is worth exactly 5% — the whole table moves in clean 5-point steps, which is why /20 scores are so easy to work out in your head. Second, the passing line is 12/20: 60% is the lowest D−, and 11/20 (55%) is already an F. Third, the grade bands are unevenly spaced in question terms: it takes only 2 correct answers to climb from a B (17/20) to an A (19/20), but 5 correct answers to climb from an F to a D− (11/20 to 12/20 crosses the line, but the F band itself spans 0–11).
Teachers love the /20 table for the same reason students do: it is the grading chart for the most common quiz size in school. If you want the same treatment for the other common sizes, see our full walkthroughs of 16 out of 20 and 11 out of 15.
Why 90% Causes Arguments: A− or A?
18/20 is the most argued-about score in the /20 family, and the argument is never about the math — everyone agrees it is 90%. The argument is about what 90% means.
On a plus/minus scale, 90% is an A−. The A band is split into three steps — A+ (97–100), A (93–<97), A− (90–<93) — and 90% is the floor of the lowest of the three. On a straight scale (90/80/70/60 with no plus or minus), 90% is a plain A, because the A band starts at 90% and runs all the way to 100%.
Then there are the schools that shift the cutoffs. Some use A = 93%, A− = 90% (the scale in this guide). Others use A = 92%, A− = 90%. A few use A = 94%. And some schools round: a teacher who records 89.6% might round it up to 90% and call it an A−, while another records exactly what the numbers say. The practical upshot is simple: if you got 18/20, your grade is an A-range grade on every scale in common use — the only question is whether it carries a minus, and that is decided by your school’s published scale, not by the score itself.
Why does the minus matter? Because of GPA points. An A is worth 4.0 grade points; an A− is worth 3.7. Over a semester of courses, the difference between a 4.0 and a 3.7 in one class moves a GPA by about 0.06 per course — small for one class, noticeable across five or six. It also matters for cutoffs: some honors programs and scholarships draw their line at a 3.7 GPA, which is exactly the A− value. An 18/20 is never a bad result, but it is worth knowing which side of the line you are on.
Is 18/20 a Good Grade?
Yes — by any reasonable measure, 18/20 is a very good grade. You answered 90% of the questions correctly, you are in the A range on every common scale, and you earned 3.7 GPA points out of a possible 4.0. On a 20-question test, you missed only 2 questions.
Here is the context that makes it concrete. In most classes, the average test score sits somewhere in the 70s — a C range. A 90% is roughly 15–20 points above a typical class average, which puts it in the top quarter of most classrooms. It is also comfortably above every common threshold that matters: the 80% line for a B, the 85% line many teachers use for honors work, and the 90% line for the A range itself.
The one honest caveat: “good” depends on what the test was. An 18/20 on a hard exam where the class average was 12/20 is outstanding. An 18/20 on a take-home quiz where most of the class scored 20/20 is merely solid. Grades are relative to the class as well as to the scale, and a teacher who curves grades might move an 18/20 even higher if the whole class struggled. But on the raw numbers alone, 18/20 is a grade to be pleased with.
What Does 18/20 Do to Your GPA?
As a single assignment, 18/20 contributes 3.7 grade points if your school uses the plus/minus scale — or 4.0 if your school uses a straight scale. How much that moves your overall GPA depends on the course’s credit weight and how many other courses you are taking.
A quick example. Suppose you are taking five 3-credit courses (15 credits total) and your other four courses are all B’s (3.0 each). With an A− (3.7) in the fifth course, your GPA is (3.0 + 3.0 + 3.0 + 3.0 + 3.7) ÷ 5 = 15.7 ÷ 5 = 3.14. If that fifth course had been a plain A (4.0) instead, your GPA would be 16.0 ÷ 5 = 3.20. The difference between an A− and an A in one course out of five is 0.06 GPA points — real, but small. The bigger lever is always the number of A-range grades, not whether one of them carries a minus.
If you want to run your own numbers, our GPA calculator averages any set of letter grades, and our cumulative GPA calculator shows how this term folds into your overall GPA. For the benchmarks — what counts as a good GPA in high school versus college — see what is a good GPA.
Worked Examples: 18/20 in Real Grade Math
Example 1: 18/20 on a test worth 25% of your final grade
Your test score contributes its percentage times its weight to your final grade: 90% × 0.25 = 22.5 points out of the 25 available. If the rest of your coursework averages 80%, that part contributes 80% × 0.75 = 60 points, and your final grade is 22.5 + 60 = 82.5% — a B−. One strong test at 90% lifted an 80% average by 2.5 points. That is the weight effect: a single test only moves the final grade as far as its weight allows.
Example 2: How much does one more question matter?
On a 20-question test, each question is worth 5%. So the difference between 17/20 and 18/20 is the difference between 85% (B) and 90% (A−) — a full letter band and 0.7 GPA points, from a single question. And the difference between 18/20 and 19/20 is the difference between an A− (3.7) and an A (4.0). On short tests, every question is expensive: there are no cheap misses. This is the same reason a 20-question quiz feels so much harsher than a 100-question exam, where each question is worth only 1%. For the full picture of how many misses each grade allows on every test size, see how many questions you can miss and still pass.
Example 3: Recovering from a bad test with an 18/20
Suppose you scored 14/20 (70%, C−) on the first test and 18/20 (90%, A−) on the second, and both tests count equally. Your average is (70 + 90) ÷ 2 = 80% — a B−. The strong second test pulled the average up 10 points from the first test’s 70%. But notice it did not erase the first test: you would need a 100% on the second test to average 85%. Recovery math is always like this — a great score helps, but it shares the average with the bad one. To find exactly what you need on the next test to hit a target grade, use our final grade calculator.
Half Points, Extra Credit, and Rounding on /20 Tests
Real /20 tests are rarely as clean as the table. Three wrinkles change the number:
Half points
If your teacher gives half credit for a partially correct answer, your score can land between the table’s rows — 17.5/20, for example. That is 87.5%, which is a B+ on the plus/minus scale (87–<90). Half points matter most exactly at the boundaries: 17.5/20 is a B+, but a teacher who rounds it to 18/20 would record an A−. Whether half points exist, and whether they are rounded, is entirely your teacher’s policy — ask before the test, not after.
Extra credit
Some 20-question tests carry a bonus question, so the total possible is 21 or 22 while the paper is still called “out of 20.” If you scored 18/20 plus 2 extra credit points, your percentage is 20 ÷ 20 = 100% (most schools cap at 100%). If the extra credit is counted on top of the 20, 18 correct plus 2 bonus is 20/20 = 100% — an A+. Extra credit is the one way to beat the table, and it is why the same 18 correct answers can produce different grades in different classrooms. We have a full guide on how extra credit affects your grade.
Rounding
Some teachers round 89.5% up to 90%; some record 89.5% as it is; some only round if you ask. On a /20 test, rounding rarely matters, because every score is a clean multiple of 5% — there is no 89.5% on a 20-question test unless half points are involved. But on a 40-point test, where each question is worth 2.5%, an 89.5% is possible (35.8/40 is not a real score, but 35.5/40 with half points is 88.75%). The rule to remember: rounding policies are set by the teacher, and the safe assumption is always that there is no rounding.
18/20 vs. the Neighbouring Scores
The scores around 18/20 are the ones students compare it against, and the comparisons show how steep the /20 scale is:
- 19/20 (95%, A, 4.0): one more correct answer. The gap between an A− and an A is a single question — and 0.3 GPA points.
- 17/20 (85%, B, 3.0): one fewer correct answer. The gap between an A− and a B is also a single question — but 0.7 GPA points, because it crosses the A/B boundary and skips the B+ band entirely (there is no 87.5% on a clean /20 test).
- 16/20 (80%, B−, 2.7): two fewer correct answers, a full point lower in GPA terms. See our full guide to what grade 16/20 is.
- 18/20 vs. 45/50 (90%, A−): the same percentage and the same letter grade, but a different test. On a 50-question test each question is worth 2%, so 45/50 has more room for error than 18/20 — you can miss 5 questions and still hold 90%, versus only 2 on a 20-question test.
That last comparison is the one that surprises people: the same 90% is easier to hold on a longer test, because each miss costs less. A student who scores 90% on a 50-question exam has absorbed 5 wrong answers; a student who scores 90% on a 20-question quiz has absorbed only 2. Same grade, different achievement — which is why teachers weight longer tests more heavily.
Frequently Asked Questions
What grade is 18/20?
18/20 is 90%, which is an A− on the standard plus/minus scale (A− = 90–<93), worth 3.7 GPA points. On a straight 90/80/70/60 scale with no plus or minus, the same score is a plain A, worth 4.0 points.
Is 18/20 an A or an A−?
Both — it depends on the scale. On the plus/minus scale most US schools use, 90% is the bottom of the A− band, so it is an A−. On a scale without plus/minus grades, 90% is the bottom of the A band, so it is an A. Check your school’s scale or your syllabus to know which one applies to you.
Is 18/20 a good grade?
Yes. It is 90% correct, in the A range on every common scale, and well above the typical class average (usually in the 70s). You missed only 2 questions out of 20. The only scores that beat it on a /20 test are 19/20 (95%, A) and 20/20 (100%, A+).
What is 18/20 as a GPA?
On the standard 4.0 scale, 18/20 is worth 3.7 grade points (the A− value). On a straight scale with no plus/minus, it is worth 4.0. One course’s grade points only move your overall GPA by a fraction — five courses averaging 3.7 give a 3.7 GPA — so the difference between an A− and an A in a single course is about 0.06 GPA points.
How do I calculate 18 out of 20 as a percentage?
Divide 18 by 20 and multiply by 100: 18 ÷ 20 = 0.9, and 0.9 × 100 = 90%. The same formula works for any score: correct ÷ total × 100. For any test size, our test grade calculator does it in one click.
Does 18/20 round up to an A?
No — 90% is exactly the A− floor on the plus/minus scale, so there is nothing to round. Rounding only helps scores that sit just below a boundary, like 89.5%. On a clean /20 test every score is a multiple of 5%, so 18/20 is precisely 90% and precisely an A− (or a plain A on a straight scale). A teacher who wants to give you an A for an 18/20 is using a straight scale, not rounding.
The One-Paragraph Version
18/20 is 90% — an A− (3.7 GPA points) on a plus/minus scale, a plain A (4.0) on a straight 90/80/70/60 scale. Each question on a 20-question test is worth 5%, so the difference between an A− and a B is a single question, and the difference between an A− and an A is a single question the other way. It is a very good grade by any measure, and the only thing that decides whether it carries a minus is your school’s scale. If you want the same answer for any other score, our letter grade calculator converts any percentage or points score to a letter grade, and our test grade calculator builds the full chart for any test size.
