Grid options
                                While Bootstrap uses ems or rems for defining most sizes,pxs are used for grid breakpoints and container widths. This is because the viewport width is in pixels and does not change with the font size.
                            
See how aspects of the Bootstrap grid system work across multiple devices with a handy table.
| Extra small <576px | Small ≥576px | Medium ≥768px | Large ≥992px | Extra large ≥1200px | |
|---|---|---|---|---|---|
| Max container width | None(auto) | 540px | 720px | 960px | 1140px | 
| Class prefix | .col- | .col-sm- | .col-md- | .col-lg- | .col-xl- | 
| # of columns | 12 | ||||
| Gutter width | 30px(15px on each side of a column) | ||||
| Nestable | Yes | ||||
| Column ordering | Yes | ||||
Equal-width
                                For example,here are two grid layouts that apply to every device and viewport,from xsto xl. Add any number of unit-less classes for each breakpoint you need and every column will be the same width.
                            
Example:Stacked-to-horizontal
                                Using a single set of .col-md-*grid classes,you can create a default grid system that starts out stacked on mobile devices and tablet devices(the extra small to small range) before becoming horizontal on desktop(medium) devices. Place grid columns in any .row.
                            
Example:Mobile and desktop
                                Don't want your columns to simply stack in smaller devices? Use the extra small and medium device grid classes by adding .col-xs-* .col-md-* to your columns. See the example below for a better idea of how it all works.
                            
Example: Mobile, tablet, desktops
                                Build on the previous example by creating even more dynamic and powerful layouts with tablet .col-sm-* classes.
                            
Responsive column resets
                                With the four tiers of grids available you're bound to run into issues where, at certain breakpoints, your columns don't clear quite right as one is taller than the other. To fix that,use a combination of a .clearfixand our responsive utility classes.
                            
Resize your viewport or check it out on your phone for an example.
Offsetting columns
                                Move columns to the right using .offset-md--*classes. These classes increase the left margin of a column by *columns. For example,.offset-md-4moves .col-md-4over four columns.
                            

