12-column grid model in Bootsrap - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the 12-column grid model in Bootstrap?

It is a layout system that divides the page width into 12 equal parts called columns. You can combine these columns to create different widths for content blocks.

beginner

How do you create a row in Bootstrap's 12-column grid?

Use the class="row" on a container element. This groups columns horizontally and ensures proper spacing.

beginner

How do you specify the width of a column in Bootstrap's grid?

Add a class like <code>col-*</code> where * is a number from 1 to 12. For example, <code>col-6</code> means the column takes 6 out of 12 parts, or half the width.

intermediate

Why is the 12-column grid model useful for responsive design?

Because 12 can be divided evenly many ways (2, 3, 4, 6), it lets you easily create layouts that adjust well on different screen sizes.

intermediate

What happens if the total column widths in a row exceed 12?

The columns will wrap to the next line, which can break your layout. Always keep the total column count per row at 12 or less.

In Bootstrap's 12-column grid, what class would you use for a column that takes one quarter of the row's width?

A col-3

B col-4

C col-6

D col-9

Since 12 divided by 4 is 3, a quarter width column uses col-3.

What is the purpose of the row class in Bootstrap's grid?

A To create horizontal groups of columns

B To add padding inside columns

C To set font size

D To add background color

The row class groups columns horizontally and manages spacing between them.

If you want two equal columns side by side in Bootstrap's grid, which classes would you use?

A col-4 and col-8

B col-6 and col-6

C col-3 and col-9

D col-12 and col-12

Two columns each with col-6 take half the width each, fitting side by side.

What happens if you add three columns with classes col-5, col-5, and col-5 inside one row?

A The row breaks and disappears

B All columns fit in one line

C The third column wraps to the next line

D Columns overlap

Because 5+5+5=15 which is more than 12, the third column moves to the next line.

Why is the number 12 chosen for the grid columns in Bootstrap?

A Because 12 is the default font size

B Because 12 is the number of months in a year

C Because 12 is a prime number

D Because 12 divides evenly into many parts

12 divides evenly into halves, thirds, quarters, sixths, making flexible layouts easier.

Explain how the 12-column grid model helps create flexible page layouts in Bootstrap.

Think about how dividing a page into parts helps arrange content.

Describe what happens if the total column widths in a Bootstrap row exceed 12 and how to avoid layout issues.

Consider how space is limited in one row.

Practice

1. In Bootstrap's 12-column grid system, how many columns can you combine in a single row without breaking the layout?

easy

A. Only 3 columns maximum

B. Exactly 6 columns only

C. Up to 12 columns combined

D. Any number of columns without limit

Solution

1. Step 1: Understand the 12-column grid concept

   The grid divides the page width into 12 equal parts, so columns in a row must add up to 12 or less.

2. Step 2: Apply the rule to column combinations

   You can combine columns as long as their total width does not exceed 12, ensuring the layout fits perfectly.

3. Final Answer:

   Up to 12 columns combined -> Option C

4. Quick Check:

   Sum of columns ≤ 12 = Up to 12 columns combined [OK]

Hint: Remember total columns per row must be 12 or less [OK]

Common Mistakes:

• Thinking you can use more than 12 columns in one row
• Assuming exactly 6 columns are required
• Believing any number of columns works

2. Which of the following is the correct Bootstrap class to create a column that spans 4 out of 12 columns?

easy

A. col-6

B. col-12

C. col-8

D. col-4

Solution

1. Step 1: Identify the class for column width

   Bootstrap uses classes like col-4 to specify a column that spans 4 of the 12 grid columns.

2. Step 2: Match the class to the required width

   Since we want 4 columns wide, col-4 is the correct class.

3. Final Answer:

   col-4 -> Option D

4. Quick Check:

   Class for 4 columns = col-4 [OK]

Hint: Class name matches number of columns (col-4 for 4 columns) [OK]

Common Mistakes:

• Using col-12 which spans full width
• Choosing col-8 or col-6 which are wider than 4 columns
• Confusing col-4 with col-14 (invalid)

3. What will be the layout result of this Bootstrap row?

<div class="row">
  <div class="col-3">A</div>
  <div class="col-6">B</div>
  <div class="col-3">C</div>
</div>

medium

A. Three columns in one row with widths 3, 6, and 3

B. Two rows because columns exceed 12

C. One column spanning full width

D. Columns stacked vertically

Solution

1. Step 1: Calculate total column width in the row

   Sum of columns: 3 + 6 + 3 = 12, which fits exactly in one row.

2. Step 2: Understand Bootstrap layout behavior

   Since total is 12, all columns appear side by side in one row with widths proportional to 3, 6, and 3.

3. Final Answer:

   Three columns in one row with widths 3, 6, and 3 -> Option A

4. Quick Check:

   Total columns = 12 means one row layout [OK]

Hint: Add column numbers; if 12 or less, same row [OK]

Common Mistakes:

• Assuming columns exceed 12 and wrap to next row
• Thinking columns stack vertically by default
• Believing only one column shows

4. Identify the error in this Bootstrap grid code:

<div class="row">
  <div class="col-5">X</div>
  <div class="col-8">Y</div>
</div>

medium

A. Total columns exceed 12, causing layout break

B. Missing closing tag for row

C. Incorrect class names used

D. No error, layout is correct

Solution

1. Step 1: Add column widths to check total

   5 + 8 = 13, which is more than 12 allowed per row.

2. Step 2: Understand Bootstrap grid rules

   When total exceeds 12, columns wrap or break layout, causing unexpected results.

3. Final Answer:

   Total columns exceed 12, causing layout break -> Option A

4. Quick Check:

   Sum > 12 means layout error [OK]

Hint: Sum columns; if over 12, layout breaks [OK]

Common Mistakes:

• Ignoring total column width sum
• Thinking 5 and 8 fit in one row
• Assuming class names are wrong

5. You want to create a responsive layout with three columns: first takes 3 columns on small screens and 6 on medium, second takes 6 on small and 3 on medium, third takes 3 on small and 3 on medium. Which Bootstrap classes correctly achieve this?

hard

A. col-md-3 col-sm-6, col-md-6 col-sm-3, col-md-3 col-sm-3

B. col-sm-3 col-md-6, col-sm-6 col-md-3, col-sm-3 col-md-3

C. col-3 col-6, col-6 col-3, col-3 col-3

D. col-sm-6 col-md-3, col-sm-3 col-md-6, col-sm-3 col-md-3

Solution

1. Step 1: Match small screen classes

   First column: 3 columns on small = col-sm-3, second: 6 columns = col-sm-6, third: 3 columns = col-sm-3.

2. Step 2: Match medium screen classes

   First column: 6 columns on medium = col-md-6, second: 3 columns = col-md-3, third: 3 columns = col-md-3.

3. Step 3: Verify option matches all classes

   col-sm-3 col-md-6, col-sm-6 col-md-3, col-sm-3 col-md-3 matches all these class assignments correctly.

4. Final Answer:

   col-sm-3 col-md-6, col-sm-6 col-md-3, col-sm-3 col-md-3 -> Option B

5. Quick Check:

   Responsive classes match screen sizes [OK]

Hint: Use col-sm-* for small, col-md-* for medium screens [OK]

Common Mistakes:

• Mixing up small and medium class prefixes
• Using col-* without breakpoint for responsiveness
• Swapping column sizes between breakpoints