Bar Charts
A bar chart uses bars of equal width to show the frequency of each category. The taller the bar, the higher the frequency.
A bar chart is one of the most common ways to display categorical data. Each category gets its own bar, and the height (or length) of the bar shows the frequency.
When drawing a bar chart you should:
- label both axes clearly
- give the chart a title
- use equal-width bars with equal gaps between them
- use an even scale on the frequency axis, starting at 0
To read a bar chart, find the top of the bar and read across to the frequency axis.
Watch it work
Question: The table below shows the favourite fruit of 24 pupils. Draw a bar chart.
Apple: 8, Banana: 6, Orange: 4, Grape: 6.
Step 1: Draw horizontal and vertical axes. Label the vertical axis "Frequency" (going up to at least 8) and the horizontal axis with the fruit names.
Step 2: Draw a bar for each fruit at the correct height: Apple up to 8, Banana up to 6, Orange up to 4, Grape up to 6.
Step 3: Check that the bar heights add up: . This matches the total, so the chart is correct.
Have a go
Q1. In a bar chart, the bar for "Tennis" reaches up to 12 on the frequency axis. How many people chose tennis?
12 people.
Q2. A bar chart shows Red = 7, Blue = 11, Green = 5. How many items are there in total?
Q3. Why must the frequency axis on a bar chart start at 0?
If it does not start at 0, the bar heights give a misleading impression of the differences between categories.
Q4. Can you use a bar chart for numerical data such as test scores (0–100)? Explain.
Not directly — individual scores would give too many bars. You would need to group the scores into class intervals first, which gives a different type of chart.