A relative frequency distribution is the proportion or fraction of times a value occurs in a data set. To find the relative frequencies, one can divide each frequency by the total number of data points in the sample. It is very similar to a regular frequency distribution, except that instead of reporting how many data values fall in a class, a relative frequency distribution reports the fraction of data values that fall in a class. These fractions or proportions are called relative frequencies and can be given as fractions, decimals, or percents.

Admittedly, there is not much difference in constructing a relative frequency distribution from constructing a regular frequency distribution. The starting process is the same, and the same guidelines must be used when creating classes for the data. The only key difference between a frequency distribution graph and a relative frequency distribution graph is that the vertical (y-axis) axis uses proportional or relative frequency rather than simple frequency.

Relative frequency distributions are often displayed in frequency polygons and in histograms.