A percentile (or a centile) is a measure in statistics.

It shows the value below which a given percentage of observations falls. For example, the 20th percentile is the value (or score) below which 20% of the observations may be found.

In statistics a large set of numerical data is sometimes divided into 100 groups, each with 1% of the data. The data are arranged in ascending order. Each of the 99 dividing points is called a percentile of the data set.

The 35th percentile, for instance, is the value of all observations below 35% of the datapool.

Some of the percentiles have special names. The 25th, 50th and 75th percentiles are called quartiles. The 50th percentile is also called the median.