A bar chart displays data as separate rectangular bars, with a gap between each one, where the height or length of a bar shows the frequency or value for that category. To read one, find the category on one axis, then read across or up to the bar and off to its value on the scale.
Example 1 — Read the bar chart: How many students chose Swimming?
Step 1
Find the "Swimming" bar on the x-axis
Step 2
Read the height of the bar across to the y-axis scale
Step 3
The bar reaches 18. Answer: 18 students
Example 2 — Which sport is the most popular? How many more students chose Football than Running?
Step 1
Most popular = tallest bar = Football (25 students)
Step 2
Difference = \(25 - 8 = \mathbf{17}\) more students chose Football than Running
Reading tip: If a bar falls between gridlines, estimate the value carefully. A bar halfway between 10 and 15 = 12 or 13 — state which it is closest to.
✓ Quick Check 1 — Reading bar charts
Question 1 of 10
Drawing Bar Charts Accurately
A well-drawn bar chart has specific features. In an exam you will lose marks for missing any of these. Follow this checklist every time you draw a bar chart.
Bar Chart Drawing Checklist:
☑ Title describing what the chart shows
☑ Labelled x-axis (categories) with axis title
☑ Labelled y-axis with scale starting at 0 and axis title with units
☑ Equal-width bars
☑ Equal gaps between bars
☑ Bars drawn accurately to the correct heights
Example 3 — Steps to draw a bar chart for: Mon=8, Tue=12, Wed=6, Thu=10, Fri=14
Step 1
Draw x-axis (days) and y-axis. Label both axes and add a title.
Step 2
Choose a scale for the y-axis: highest value = 14, so go up to 15 or 20. Mark equal intervals (e.g. 0, 2, 4, 6, 8, 10, 12, 14).
Step 3
Draw bars of equal width with equal gaps. Heights: Mon=8, Tue=12, Wed=6, Thu=10, Fri=14.
Step 4
Check all bars are accurate — read each height back from the chart to verify.
⚠ Common mistakes: (1) Scale not starting at 0. (2) Unequal bar widths. (3) Missing axis labels or title. (4) Bars touching with no gaps.
✓ Quick Check 2 — Drawing bar charts accurately
Question 1 of 10
Compound and Grouped Bar Charts
A compound bar chart (also called a grouped bar chart) places two or more bars side by side for each category. This makes it easy to compare two groups across multiple categories. A key (legend) is essential to identify which bar represents which group.
Example 4 — Read the grouped bar chart: Did sales increase from 2023 to 2024 in every quarter?
Step 1
In each pair of bars, compare the blue (2023) to the yellow (2024)
Step 2
In every quarter (Q1, Q2, Q3, Q4) the yellow bar (2024) is taller than the blue bar (2023)
Step 3
Yes — sales increased in every quarter from 2023 to 2024
Example 5 — Which quarter showed the greatest increase in sales?
Step 1
Estimate the difference for each quarter: Q1 ≈ 5, Q2 ≈ 15, Q3 ≈ 5, Q4 ≈ 5
Step 2
Q2 shows the largest difference between the 2023 and 2024 bars
Step 3
Q2 had the greatest increase in sales
Exam tip: A grouped bar chart question will often ask you to compare two groups. Always state the specific values you read from the chart and say which is higher/lower by how much.
✓ Quick Check 3 — Compound and grouped bar charts
Question 1 of 10
Practice
Work out each answer, then type it in and click Check to see if you're right.
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Question
Your answer
Result
1
A bar chart shows: Monday = 15, Tuesday = 12, Wednesday = 18, Thursday = 9, Friday = 15. Which day has the highest value?
2
Using the same chart, what is the value for Thursday?
3
What is the total of all five days' values?
4
What is the difference between the highest and lowest values?
5
Which day has the lowest value?
6
How many days have a value of 15 or more?
7
What is the mean (average) of all five days? (Total ÷ 5)
⚠ Things to Watch Out For
Using the wrong scale value: Always check the scale on the y-axis carefully. If 5 squares = 20, then each square = 4. Read grid lines, not midpoints between them.
Bars touching in a bar chart: Bars in a standard bar chart have GAPS between them (for categorical data). Bars only touch in frequency diagrams (grouped continuous data).
Not labelling axes: Both axes must be labelled with the quantity AND units. Missing labels lose marks.
Compound bar chart — reading total vs individual: In a compound (stacked) bar chart, read individual sections, not just the total bar height, when asked about specific categories.
Drawing bars the wrong width: All bars must be the same width. Varying bar widths suggest different amounts of data and are misleading.