A bar chart or bar graph is a chart or graph that presents categorical data with rectangular bars with heights or lengths proportional to the values that they represent. The bars can be plotted vertically or horizontally. A vertical bar chart is sometimes called a line graph.

A bar graph shows comparisons among discrete categories. One axis of the chart shows the specific categories being compared and the other axis represents a measured value. Some bar graphs present bars clustered in groups of more than one showing the values of more than one measured variable.