A score of "X out of Y" becomes a percentage by dividing X by Y and multiplying by 100: (X ÷ Y) × 100.
Worked examples
- 40 out of 50 = (40 ÷ 50) × 100 = 80%
- 18 out of 20 = (18 ÷ 20) × 100 = 90%
- 7 out of 8 = (7 ÷ 8) × 100 = 87.5%
- 33 out of 40 = (33 ÷ 40) × 100 = 82.5%
Common results table
| Score | Percentage |
|---|---|
| 1 out of 3 | 33.33% |
| 2 out of 3 | 66.67% |
| 3 out of 4 | 75% |
| 9 out of 10 | 90% |
Where this is used
Grades, quizzes, survey completion, uptime (servers up out of total checks) and sports statistics all use the same "X out of Y" calculation.
Turning a percentage back into a score
The same formula works in reverse. If you know the percentage and the total, multiply them to recover the raw score: for a quiz of 40 questions, 80% means 0.80 × 40 = 32 correct answers. This is useful when a grade, an SLA target or a completion figure is reported as a percentage but you need the underlying count.
Rounding and repeated decimals
Some ratios never divide cleanly. 1 out of 3 is 33.333…%, and 2 out of 3 is 66.666…%. For display, round to one or two decimals, but keep the unrounded value if you will use it in further calculations — rounding early can shift a final grade or a weighted average. A score that looks like 66.67% is really two-thirds, and treating it as exactly 66.67% introduces a small error that grows when you average many results.
Weighted totals and partial credit
Real grades often combine several "X out of Y" scores. To average them fairly, convert each to a percentage first, then weight by the number of points available. A 9 out of 10 quiz and a 30 out of 50 exam are not equal: 45 points out of 60 total is the true result, which is 75%, not the 80% a simple average of 90% and 50% would suggest. Always sum the parts and the wholes before dividing.
Enter the two numbers in Mode 2 of our percentage calculator.