Spacing

Bootstrap spacing is a utility which assigns responsive margin or padding classes to elements to modify its display position.

Notation

Spacing utilities that apply to all breakpoints, from xs to xl, have no breakpoint abbreviation in them. This is because those classes are applied from min-width: 0 and up, and thus are not bound by a media query. The remaining breakpoints, however, do include a breakpoint abbreviation.

The classes are named using the format {property}{sides}-{size} for xs and {property}{sides}-{breakpoint}-{size} for sm, md, lg, and xl.

Where property is one of:

m - for classes that set margin
p - for classes that set padding

Where sides is one of:

t - for classes that set margin-top or padding-top
b - for classes that set margin-bottom or padding-bottom
l - for classes that set margin-left or padding-left
r - for classes that set margin-right or padding-right
x - for classes that set both *-left and *-right
y - for classes that set both *-top and *-bottom
blank - for classes that set a margin or padding on all 4 sides of the element

Where size is one of:

0 - for classes that eliminate the margin or padding by setting it to 0
1 - (by default) for classes that set the margin or padding to $spacer-x * .25 or $spacer-y * .25
2 - (by default) for classes that set the margin or padding to $spacer-x * .5 or $spacer-y * .5
3 - (by default) for classes that set the margin or padding to $spacer-x or $spacer-y
4 - (by default) for classes that set the margin or padding to $spacer-x * 1.5 or $spacer-y * 1.5
5 - (by default) for classes that set the margin or padding to $spacer-x * 3 or $spacer-y * 3

(You can add more sizes by adding entries to the $spacers Sass map variable.)

Examples

Here are some representative examples of these classes:

                
.mt-0 {
  margin-top: 0 !important;
}

.ml-1 {
  margin-left: ($spacer-x * .25) !important;
}

.px-2 {
  padding-left: ($spacer-x * .5) !important;
  padding-right: ($spacer-x * .5) !important;
}

.p-3 {
  padding: $spacer-y $spacer-x !important;
}

Horizontal centering

Additionally, Bootstrap also includes an .mx-auto class for horizontally centering fixed-width block level content—that is, content that has display: block and a width set—by setting the horizontal margins to auto.

Centered element

                
<div class="mx-auto" style="width: 200px;">
  Centered element
</div>