How to draw a bar graph

Why bar graphs?

Pictographs are fun, but with lots of data they take long to draw and cannot show every value exactly. A bar graph shows data with bars of equal width, placed with equal gaps, where the length or height of each bar gives the value. You can compare categories at a glance and spot the largest and smallest.

Steps to draw a bar graph

1. Draw two lines: a horizontal line and a vertical line meeting at a corner.
2. Place the categories: write them along one line, equally spaced.
3. Choose a scale: decide how many items one unit length stands for, so the longest bar fits. Mark the scale on the other line, starting from zero.
4. Work out bar lengths: length in units = value ÷ scale.
5. Draw the bars: same width, same gaps, each as long as its value.
6. Label both lines, write the scale and add a title.

Example 1: sweets (1 unit = 1 student)

Shri Nilesh’s class chose sweets: jalebi 6, gulab jamun 9, gujiya 13, barfi 3 and rasgulla 7. The numbers are small, so 1 unit length = 1 student works well.

Example 2: runs (1 unit = 10 runs)

Smriti scored 80, 50, 10, 100, 90, 0, 90 and 50 runs in eight matches. Marking every run from 0 to 100 would be tedious, so use 1 unit length = 10 runs: 80 runs is 8 units and 100 runs is 10 units. Match 6, with 0 runs, has no bar at all.

Example 3: family expenses (1 unit = ₹200)

Item	Expenditure	Bar length (÷ 200)
House rent	₹3,000	15 units
Food	₹3,400	17 units
Education	₹800	4 units
Electricity	₹400	2 units
Transport	₹600	3 units
Miscellaneous	₹1,200	6 units

The graph shows that Imran’s family spends most on food and next most on house rent. Electricity (₹400) is exactly half of education (₹800), and education is less than one-fourth of food, since one-fourth of ₹3,400 is ₹850.

Reading a bar graph

In a Delhi traffic study, a bar graph with 1 unit = 100 vehicles showed about 150 vehicles from 6 to 7 a.m., 1,200 from 7 to 8, 1,000 from 8 to 9, 800 from 9 to 10, 700 from 10 to 11 and 600 from 11 to noon: about 4,450 in all. The longest bar, 7 to 8 a.m., is the rush hour, when people head to work and school.

Spotting mistakes

Always check bars against the data. In a graph of tickets sold at Bhopal station, the bar for Vidisha was 6 units for 24 tickets, so the scale was 1 unit = 4 tickets; Indore’s 28 tickets should then be 7 units, not shorter.

Vertical or horizontal?

Both are correct, but choose what suits the data. Heights rise from the ground, so the tallest mountain on each continent looks natural as vertical bars, a column graph. Lengths lie along the ground, so river lengths suit horizontal bars.

Beware of misleading pictures

Infographics decorate graphs with artistic images. They catch attention, but can mislead. Drawn as triangles, a taller mountain also becomes wider and looks far bigger than it is. Everest (8,848 m) is not twice as tall as Elbrus (5,642 m): 5,642 × 2 = 11,284.

To organise data before graphing, read tally marks; for picture graphs, read what is a pictograph. For the textbook’s questions, see the Chapter 4 NCERT solutions; for the whole chapter, see the Chapter 4 notes.