The basic formula
A test score as a percentage is the points you earned divided by the points possible, multiplied by 100. If every question is worth one point, points earned is simply the number of questions you got right.
Score % = (points earned ÷ points possible) × 100.
- 17 of 20 right: 17 ÷ 20 = 0.85, so the score is 85%.
- 42 of 50 points: 42 ÷ 50 = 0.84, so the score is 84%.
Starting from the number wrong
Teachers often count the wrong answers because there are fewer of them. Subtract the wrong answers from the total to get the number right, then use the same formula.
Example: a 25-question test with 3 wrong. 25 − 3 = 22 right, and 22 ÷ 25 = 0.88, so the score is 88%. Each wrong answer on a 25-question test costs 4 percentage points, because 100 ÷ 25 = 4.
Partial credit and half points
When a question can earn partial credit, add the points first and then divide. A 20-point test where a student earns 18.5 points is 18.5 ÷ 20 = 0.925, or 92.5%.
On a 20-point test, a half point is worth 2.5 percentage points (0.5 ÷ 20 × 100). On a 50-point test it is worth 1 percentage point. The fewer points a test has, the more each half point matters.
Rounding the result
Many people round half up: 87.5% becomes 88%, and 84.4% stays 84%. Some teachers round to the nearest whole number, some keep one decimal, and some drop the decimals without rounding. Your teacher or school policy decides, so check before you assume a score of 89.6% counts as 90%.
Rounding matters most near a letter-grade cutoff, which is covered in the guide on letter grade scales.
Writing the score as a fraction
A score can be written as a fraction, such as 22/25, or as a percent, 88%. They say the same thing. Put the fraction in the gradebook when the point total changes from test to test, and convert to a percent when you want to compare tests of different lengths.
The grading chart on this site lists the percent for every number of wrong answers for a test of any length, including half points, so you can look up a result instead of dividing each time.
Have a correction or a suggestion? Tell the studio.