Box plots are typically a rectangular shape (like a bar), with a line somewhere within the box that represents the centre of a distribution of data values – typically the median. The length of the box represents the range of values in the distribution, with the upper bound equalling the highest value and the lower bound equalling the lowest value. Thus, long boxes indicate a wide distribution of data values for that measurement. Boxes can be drawn horizontally or vertically.

Box plots are used in many scientific fields for multiple trials of the same experiment, to show consistencies (or inconsistencies), and multiple trials of different experiments, to show changes, trends or patterns.

Box plots may have lines extending from the boxes called whiskers. Box-and-whisker plots are a specific kind of box plot that show the distribution of data values with box points – the first middle point (median) and the middle points of the 2 halves (25th and 75th percentiles) – and also show other values, such as the minimum and maximum of all the data: