About this calculator
Different textbooks and software use slightly different rules. Choose the Excel / Google Sheets method to match a spreadsheet, or the (n + 1) rule used in many textbooks.
How to use it
- Enter the numbers.
- Enter the percentile.
- Optionally enter a value to find its percentile rank.
The formula
PERCENTILE.INC: position = (n − 1) × p + 1; (n + 1) rule: position = (n + 1) × p
- p
- percentile as a fraction
- n
- number of values
Worked example
90th percentile of 2, 4, 4, 5, 7, 9, 10, 12, 15, 18
- Position = 9 × 0.9 + 1 = 9.1.
- Between the 9th value (15) and the 10th (18): 15 + 0.1 × 3 = 15.3.
What the result means
A percentile is about position, not a percentage of marks: scoring at the 90th percentile means doing better than 90% of the group.
Assumptions
- Real numbers.
Limitations
- The (n + 1) rule cannot give percentiles very close to 0 or 100 for small data sets.
Frequently asked questions
What is the difference between percentage and percentile?
A percentage is a score out of 100. A percentile is a rank: the share of people scoring below you.
Why do Excel and my textbook differ?
They use different position rules. Both are valid; pick the one your course or report uses.
What is the percentile rank?
The percentage of values below a value, counting equal values as half.
Last reviewed on 6 October 2026. Found a mistake? Tell us.