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Different question values? Add their points first. Extra credit can take the score above 100%.
What is 13 out of 18 as a percentage?
13 out of 18 (13/18) is 72.22%, a C- 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
13/18 ≈ 0.722222
13/18 cannot be reduced. Divide 13 earned points by 18 possible points, then multiply by 100 to get 72.22%. 18 − 13 = 5 points missed.
Or count by points: each point is worth 100 ÷ 18 ≈ 5.5556%, so 13 × 5.5556 ≈ 72.22%.
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 |
|---|---|---|
| 12 out of 18 | ≈ 66.67% | 6 |
| 13 out of 18 | ≈ 72.22% | 5 |
| 14 out of 18 | ≈ 77.78% | 4 |
≈ means rounded to 2 decimal places.
One point changes this score by 5.5556 percentage points. The denominator stays 18.