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Different question values? Add their points first. Extra credit can take the score above 100%.
What is 18 out of 21 as a percentage?
To find 18 out of 21 (18/21) as a percentage, divide 18 by 21 and multiply by 100: 18 ÷ 21 × 100 ≈ 85.71%, a B on the common US plus/minus scale. Rounded to 2 decimal places.
Letter scale: Common US plus/minus scale
The plus/minus cutoffs Wikipedia lists for US colleges: A+ from 97%, A 93, A- 90, B+ 87, B 83, B- 80 and so on down to D- at 60. It is not universal, so use your syllabus's cutoffs when they differ. Source: Wikipedia, “Academic grading in the United States”.
| Letter | Lowest % | Remove |
|---|
Each letter starts at its lowest percentage and runs up to the next letter.
Rounding and decimal places
Follow your syllabus. A displayed percentage can round up while the unrounded score stays below a cutoff.
Only changes how results are shown. Extra places appear when rounding would push a score over a letter cutoff.
A letter typed as a score counts as the lowest percentage for that letter on this scale. Use the original percentage when you have it.
Check a single cutoff with the grading scale calculator.
Grading scales checked . Sources are at the bottom of the page.
The fraction, decimal and missing points
18/21 = 6/7 ≈ 0.857143
Divide 18 earned points by 21 possible points, then multiply by 100 to get 85.71%. 21 − 18 = 3 points missed.
Or count by points: each point is worth 100 ÷ 21 ≈ 4.7619%, so 18 × 4.7619 ≈ 85.71%.
The letter above uses the common US plus/minus scale. Your class may set other cutoffs: open “Letter scale” above to choose another scale or enter your own. For the general method, see how to turn points into a percentage.
What does one more point change?
| Points earned | Percentage | Points missed |
|---|---|---|
| 17 out of 21 | ≈ 80.95% | 4 |
| 18 out of 21 | ≈ 85.71% | 3 |
| 19 out of 21 | ≈ 90.48% | 2 |
≈ means rounded to 2 decimal places.
One point changes this score by 4.7619 percentage points. The denominator stays 21.