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Grid System
In a nutshell, Bootstrap grid system helps you create mobile-first layouts. Mobile first means that the grid layout will automatically be responsive for smaller screens. The HTML then defines the grid layout for larger screens. It comprises of a system of rows and columns to help you structure your content.
Rows are horizontal groups of columns, and each page has a maximum of 12 columns per row. Within each row, the content is placed inside the columns and it can span anywhere between 1 to 12 columns.
Bootstrap has five different types of grid tiers: Extra small, Small, Medium, Large, and Extra large. There is a breakpoint defined for each of these grid tiers.
Bootstrap uses pixels to define the grid tier breakpoints.
How it works
Container
The container is the outer most element that contains your grid. Use container for a fixed-width container in the middle of the screen (add an extra margin on larger screens) or container-fluid for full width.
<div class="container"></div>
Row
Use row to group your columns. This will keep everything lined up properly and help you structure your grid.
<div class="row"></div>
Columns
Column classes indicate the number of columns you’d like to use out of the possible 12 per row. For example col-sm-6 would mean your columns use up half the width of the row on a small screen, and col-lg-4 would use up a third on a large screen.
Here is how you would define a class prefix to use up one column width on the various screen sizes:
- Extra Small
col-1 - Small
col-sm-1 - Medium
col-md-1 - Large
col-lg-1 - Extra Large
col-xl-1
<div class="col-sm-1"></div>
Example
A full width grid that has four columns, each taking up a full row on xs screens, half a row on sm and md screens, and a quarter of the width of the row on screens that are large and above:
<div class="container-fluid">
<div class="row">
<div class="col-12 col-sm-6 col-lg-4">First Column</div>
<div class="col-12 col-sm-6 col-lg-4">Second Column</div>
<div class="col-12 col-sm-6 col-lg-4">Third Column</div>
<div class="col-12 col-sm-6 col-lg-4">Forth Column</div>
</div>
</div>
Note that col-md and col-xl are not defined, where a size is not defined, it will default down to the next smaller size that has been specified.
Bootstrap provides a ready-made 12 column grid system for use in layouts. Consider the following code.
<div class="container">
<div class="row">
<div class="col-md-6">Content</div>
<div class="col-md-6">Content</div>
<div>
</div>
where:
- col = column
- md = screen size
- 6 = column width
As a 12 column grid system, all user defined grid column widths must add up to 12.
Screen size values can be assigned as follows:
- xs - < 768px Phones
- sm - < 992px Tablets
- md - < 1200px Laptops
- lg - > 1200px Desktops
The following code and image shows what is possible using different column widths.
<div class="container">
<div class="row">
<div class="example col-md-6">Content</div>
<div class="example col-md-6">Content</div>
<div>
</div>
<div class="container">
<div class="row">
<div class="example col-md-4">Content</div>
<div class="example col-md-4">Content</div>
<div class="example col-md-4">Content</div>
<div>
</div>
<div class="container">
<div class="row">
<div class="example col-md-3">Content</div>
<div class="example col-md-3">Content</div>
<div class="example col-md-3">Content</div>
<div class="example col-md-3">Content</div>
<div>
</div>
<div class="container">
<div class="row">
<div class="example col-md-2">Content</div>
<div class="example col-md-2">Content</div>
<div class="example col-md-2">Content</div>
<div class="example col-md-2">Content</div>
<div class="example col-md-2">Content</div>
<div class="example col-md-2">Content</div>
<div>
</div>
<div class="container">
<div class="row">
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
<div class="example col-md-1">Content</div>
</div>
</div>
More Information:
This guide is based on Bootstrap v4 (it will work with v3 except extra small screens are defined as xs and there is no xl size)
- Extra large: Viewport width >= 1200px
- Large: Viewport width >= 992px
- Medium: Viewport width >= 768px
- Small: Viewport width >= 576px
- Extra small: Viewport widths below 576px