Overview

Spacing scale

Use the spacing scale when building individual components. It includes small increments needed to create appropriate spatial relationships for detail-level designs. This scale is applied and used within all components.

Level rem px Example
Level 1 0.25 4
Level 2 0.5 8
Level 3 1 16
Level 4 1.5 24
Level 5 3 48

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
  • 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: 0.25rem !important;
}

.px-2 {
  padding-left: 0.5rem !important;
  padding-right: 0.5rem !important;
}

.p-3 {
  padding: 1rem !important;
}

Horizontal centering

Additionally, we 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>

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). 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;
}

Designing with space

Every part of a UI should be intentional including the empty space between elements. The amount of space between items creates relationships and hierarchy.

Creating relationships

Elements in a design that are near each other are seen as being meaningfully related. As more space is added between elements, their perceived relationship weakens.

Patterns created through spacing can also create relationships. Elements arranged in the same spacing pattern are seen as related pieces that have equal weight.

Space can also be used to denote groups of associated information. This creates content sections on a page without having to use lines or other graphical elements as a divider.

Creating hierarchy

Elements that have more spacing around them tend to be perceived as higher in importance than elements that have less space around them. Take this page for instance. The top level headers have more space surrounding them giving them focus and prominence. Then as the headers descend in importance they receive less space, signaling they are subordinate.

Elements that are set close to each other can be easily overlooked. Users may see the grouping but not process each individual item. Therefore, if you have an element or content of high importance on the page, consider giving it extra surrounding space to help it attract focus.

White space

Empty space — also known as white space — is important in design. It can be used to break up sections on a page or to help create focus on certain element(s). White space helps with information processing; too much dense information can be disorienting or overwhelming for a user. Sections of a UI are allowed to be dense, but the whole page should not be crowded; there should be white space to let the user’s eye rest.