Rectangular bars with lengths proportional to the values they represent.

A bar graph compares values across categories. Each bar's height (or length) shows the value for one category, so differences can be read quickly by comparing bars against the scale on the axis.

Types of bar graphs

• Simple bar graph: one bar per category.
• Grouped (multiple) bar graph: several bars per category, one for each series such as year or product.
• Stacked bar graph: segments piled in one bar so the bar height shows the total and each segment shows a part.

Reading a bar graph

• Read the title, axis labels, legend, and units first.
• Check the scale: the axis may not start at zero or may use thousands or millions.
• For a stacked bar, a segment's value is its own height, not the level of its top edge.

Common calculations

• Difference: larger bar value - smaller bar value.
• Percentage change: (new - old) / old x 100.
• Share of a total: bar value / total x 100.
• Average: sum of the relevant bars / number of bars.
• Ratio: compare two bar values and simplify.

How to solve questions

1. Identify what is asked and which bars and series are involved.
2. Read each required value accurately from the axis scale.
3. Apply the correct formula, keeping units consistent.
4. Check that the answer is reasonable against the graph.