Bootstrap Grid System

The Bootstrap grid system is the fastest and easy way to create a layout.

What is Bootstrap Grid System

Bootstrap grid system provides the quick and easy way to create responsive website layouts. As opposed to the previous Bootstrap 2.x grid system which is fixed by default, the new version, i.e. Bootstrap 3 introduces the responsive mobile first fluid grid system that appropriately scales up to 12 columns as the device or viewport size increases.

Bootstrap 3 includes predefined grid classes for quickly making grid layouts for different types of devices like cell phones, tablets, laptops and desktops, etc. For example, you can use the .col-xs-* class to create grid columns for extra small devices like cell phones, similarly the .col-sm-* class for small screen devices like tablets, the .col-md-* class for medium size devices like desktops and the .col-lg-* for large desktop screens. The following table summarizes some of the key features of the new grid system

Features Bootstrap 3 Grid System	Extra small devices Phones (<768px)	Small devices Tablets (≥768px)	Medium devices Desktops (≥992px)	Large devices Desktops (≥1200px)
Max container width	None (auto)	750px	970px	1170px
Grid behavior	Horizontal at all times	Collapsed to start, horizontal above breakpoints
Class prefix	.col-xs-	.col-sm-	.col-md-	.col-lg-
Max column width	Auto	~62px	~81px	~97px
Gutter width	15px on each side of a column (i.e. 30px)

Above table demonstrates one important thing, applying any .col-sm-* class to an element will not only affect its styling on small devices, but also on medium and large devices having a screen size greater than or equal to 768px (i.e. ≥768px) if .col-md-* and .col-lg-* class is not present. Similarly the .col-md-* class will not only affect the styling of elements on medium devices, but also on large devices if a .col-lg-* class is not present.

Now the question arises how to create rows and columns using this 12 column responsive grid system. The answer is pretty simple, at first create a container that acts as a wrapper for your rows and columns using the .container class, after that create rows inside the container using the .row class, and to create columns inside any row you can use the class.col-xs-*, .col-sm-*, .col-md-* and .col-lg-*. The columns are actual content area where we will place our contents. Let's put all these things into real action.

Creating Two Column Layouts

The following example will show you how to create two column layouts for small, medium and large devices like tables, laptops and desktops etc. However, on mobile phones, the columns will automatically become horizontal as default.

Since Bootstrap grid system is based on 12 columns, so to keep the columns in a one line (i.e. side by side), the sum of the grid column numbers in each row should be equal to 12. If you see the above example carefully you will find the numbers of grid columns (i.e. col-sm-*) add up to twelve (6+6, 4+8 and 3+9) for every row.

Creating Three Column Layouts

Similarly, you can create other layouts based on the above principle. The following example will typically create three column layouts for laptops and desktops screens. It also works in tablets in landscape mode if screen resolution is more than or equal to 992 pixels (e.g. Apple iPad). However, in portrait mode it will be horizontal as usual.

Bootstrap Layouts with Column Wrapping Feature

Now we are going to create more flexible layouts that changes the column orientation based on the viewport size. The following example will create a three column layout on medium devices like laptops and desktops, as well as on tablets (e.g. Apple iPad) in landscape mode, but on small devices like tablets in portrait mode, it will change into a two column layout where the third column moves at the bottom of the first two columns.