Purpose includes a wide range of shorthand responsive margin and padding utility classes to modify an element’s appearance.

Spacing scale

The spacing scale is a base-9 scale. Assign responsive-friendly margin or padding values to an element or a subset of its sides with shorthand classes. Includes support for individual properties, all properties, and vertical and horizontal properties. Classes are built from a default Sass map ranging from .25rem to 9rem.

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 * .25
• 2 - (by default) for classes that set the margin or padding to $spacer * .5
• 3 - (by default) for classes that set the margin or padding to $spacer
• 4 - (by default) for classes that set the margin or padding to $spacer * 1.5
• 5 - (by default) for classes that set the margin or padding to $spacer * 3
• 6 - (by default) for classes that set the margin or padding to $spacer * 4.5
• 7 - (by default) for classes that set the margin or padding to $spacer * 6
• 8 - (by default) for classes that set the margin or padding to $spacer * 7.5
• 9 - (by default) for classes that set the margin or padding to $spacer * 9
• auto - for classes that set the margin to auto

(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 * .25) !important;
}

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

.p-3 {
  padding: $spacer !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.

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

Negative margin

In CSS, margin properties can utilize negative values (padding cannot). As of 4.2, we’ve added negative margin utilities for every non-zero integer size listed above (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9). These utilities are ideal for customizing grid column gutters across breakpoints.

The syntax is nearly the same as the default, positive margin utilities, but with the addition of n before the requested size. Here’s an example class that’s the opposite of .mt-1:

.mt-n1 {
  margin-top: -0.25rem !important;
}

Here’s an example of customizing the Bootstrap grid at the medium (md) breakpoint and above. We’ve increased the .col padding with .px-md-5 and then counteracted that with .mx-md-n5 on the parent .row.

<div class="row mx-md-n5">
  <div class="col py-3 px-md-5 border bg-light">Custom column padding</div>
  <div class="col py-3 px-md-5 border bg-light">Custom column padding</div>
</div>