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How To Calculate Percentiles (With Examples)

By Abby McCain
Jun. 27, 2020
Last Modified and Fact Checked on:

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How to Calculate Percentiles (With Examples)

Mathematics plays an essential role in various aspects of our lives, especially in the professional realm. While complex equations learned in high school may not be regularly employed, a fundamental understanding of statistics—particularly percentiles—remains invaluable.

This article explores percentiles, illustrating their significance in your job search and professional development in 2026.

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What Is a Percentile?

A percentile is a statistical measure that indicates how a particular data point compares to the rest of the dataset. It allows you to understand relative performance within a group.

Standardized test score reports commonly use percentiles to provide insight into how an individual’s score stacks up against others. For instance, if you are in the 85th percentile, your score is better than 85% of test-takers.

This insight is crucial; a score of 90% might seem impressive, but without knowing your percentile, you can’t assess your performance relative to your peers. Understanding your percentile provides clarity on your standing within the group.

Percentiles vs. Percentages

Percentiles and percentages are often confused. A percentile indicates a data point’s relative position among others, while a percentage expresses a portion of a whole. For example, when discussing test scores or percentage increases, we typically refer to percentages.

How Are Percentiles Helpful?

Percentiles serve various purposes beyond test performance, aiding in research organization, data interpretation, and performance evaluation.

  1. In organizing research results. Consider evaluating a job offer. If a position in La Crosse, Wisconsin offers a salary of $75,000, it may seem low compared to your current $90,000 salary in New York. However, if research shows that this salary places you in the 90th percentile for La Crosse, you’d be earning well compared to the local population, taking into account the lower cost of living.

  2. In interpreting data. In data-heavy roles, percentiles can reveal underlying patterns. For instance, a realtor analyzing neighborhood statistics may initially focus on the best and worst areas. However, identifying neighborhoods within the 75th to 85th percentiles could offer appealing options that are more affordable yet still desirable.

  3. In gauging performance. For managers, percentiles provide insights into employee performance. For instance, understanding how sales representatives rank can help create incentive programs. Recognizing top performers in the 90th percentile can motivate others to strive for similar success.

Other Percentile Terms

Several mathematical terms relate to percentiles:

  • Median. The median, or 50th percentile, represents the middle value in a dataset and is often more informative than the average.

  • Quartile. Percentiles can be divided into quartiles every 25th percentile, with Q1 representing the lower quartile and Q3 the upper quartile.

  • Percentile range. This refers to the difference between two percentiles, such as the range between the 20th and 40th percentiles.

  • Interquartile range. The interquartile range (IQR) measures the spread of the middle half of data, calculated between Q1 and Q3.

How to Calculate a Percentile

To calculate a percentile, follow these steps:

  1. Arrange your data. Organize your dataset from smallest to largest.

  2. Determine the desired percentile. Refer to this value as k (e.g., k=80 for the 80th percentile).

  3. Find n. Identify the total number of data points, denoted as n.

  4. Calculate the index. Multiply k by n (e.g., for the 80th percentile with 50 data points, compute 0.8 x 50).

  5. Round the index if necessary. If the result is a decimal, round it to the nearest whole number.

  6. Locate the value in your dataset. Count to the index in your ordered data to find the corresponding percentile value.

Example of Calculating a Percentile

To illustrate, let’s find the 90th percentile using 50 test scores:

Here are the arranged scores:

54, 57, 61, 62, 64, 65, 68, 69, 70, 70, 73, 75, 76, 78, 80, 81, 81, 81, 82, 82, 82, 84, 84, 85, 85, 86, 86, 87, 87, 88, 88, 89, 89, 90, 90, 90, 91, 91, 92, 92, 93, 93, 94, 94, 95, 97, 98, 99, 99, 100

Next, find k, which is 90. The total number of scores (n) is 50. Calculate the index: 0.90 x 50 = 45. The 45th score is 95, indicating that a score of 95 places you in the 90th percentile.

Example of Calculating a Percentile Range

Finding a percentile range, like the 30-60 percentile range, uses similar steps:

Calculate the 30th percentile: 0.3 x 50 = 15
Calculate the 60th percentile: 0.6 x 50 = 30
Find the 15th and 30th numbers in the set (80 and 88).
The range is 88 – 80 = 8.

The percentile range between the 30th and 60th percentiles is 8.

Final Thoughts

Understanding concepts like standard deviations, normal distributions, and percentiles is increasingly relevant across various industries. In today’s data-driven world, the ability to analyze and interpret data is a highly sought-after skill.

Percentiles provide a valuable perspective on datasets, allowing you to uncover insights that may not be immediately evident. Mastering these concepts can enhance your professional capabilities and decision-making processes.

Never miss an opportunity that’s right for you.

Author

Abby McCain

Abby is a writer who is passionate about the power of story. Whether it’s communicating complicated topics in a clear way or helping readers connect with another person or place from the comfort of their couch. Abby attended Oral Roberts University in Tulsa, Oklahoma, where she earned a degree in writing with concentrations in journalism and business.

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