Bootstrap has a powerful mobile-first flexbox grid to build layouts of all shapes and sizes thanks to a twelve column system, five default responsive tiers, Sass variables and mixins, and dozens of predefined classes.
While Bootstrap uses em
s or rem
s for defining most sizes, px
s 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 |