Concept 4 of 9
The Bar Graph: Heights That Tell Stories
Today's big idea
Bar height stands for amount, so the scale up the side is what turns it into a number.
Comparing bars is instant, but reading an exact value waits on the scale.
How it works
👀 What's going on?
Two bars, one clearly taller than the other. You know which is bigger before you have read a single number. Getting the exact value out takes one more step.
💡 Here's the trick
Height stands for amount, so comparing is instant. Reading an exact value is not, because it depends on the scale: how many units each gridline is worth. Match the top of a bar to the scale and read across.
🪄 How to do it
- 1.Check the scale in the picture above for what one gridline is worth.
- 2.Follow the top of the bar across to the scale line beside it.
- 3.Read off the value that the top of the bar meets.
✍️ Try it
Each gridline on a graph is worth 2. One bar's top sits on the fourth gridline. Another sits halfway between the third and the fourth. What are the two values?
Four gridlines at 2 each is 8. Halfway between the third and the fourth gridlines is halfway between 6 and 8, which is 7.
⚠️ Watch out
Never count gridlines as ones. If each gridline is worth 5 and a bar reaches the fourth, the value is 20 and not 4. Checking the scale first is the whole job.
🌟 Why this matters
Bar graphs are the most common chart there is. Match results, rainfall through the year, and how many people came into a shop each day all arrive as bars.
Exam tip: Write the scale value at the top of the graph before you start, because every question underneath it depends on that one number.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“Bars: Juice 7, Milk 15, Water 9. How many MORE chose Milk than Juice?”
- 1
Find the bars in question
Milk = 15. Juice = 7.
- 2
'MORE' means subtract
To find the difference: bigger − smaller.
- 3
Calculate
15 − 7 = 8
- 4
Answer ✓
Milk has 8 more than Juice
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Match the top of each bar to the scale on the left. Taller = bigger.
Class Vote
Red
Blue
Green
Yellow
Tap the TALLEST bar.
Quick check
✅ VERIFICATION
On a bar graph each gridline stands for 5 books. A bar reaches exactly the third gridline. How many books is that?
⚡ Finish the activity above first to answer.
Keep going!
Up next: The Line Plot
The tallest pile wins. Spot patterns in seconds.