Sizing props and classes

Bootstrap v4 CSS provides several classes that control the sizing of elements, of which some of these have been translated into props on components.

Component size prop

Various components allow for an optional size (via the size prop). Below are the sizes supported via the default Bootstrap v4 CSS.

Available Sizes:

• sm small
• lg large

When no size is specified, this results in normal sized appearance (usually referred to as md).

These size values will be translated into the appropriate Bootstrap CSS class, depending on the component used on, such as .btn-<size> for buttons, .modal-<size> for modal, .form-control-<size> for form elements, .pagination-<size> for pagination buttons, etc.

Breakpoint sizes

Bootstrap v4 also includes viewport breakpoint sizes: xs, sm, md, lg, and xl. which refer to the width of the user's view port.

For details on breakpoint sizes, please check the Layout and Grid documentation.

Sizing utility classes

Easily make an element as wide or as tall (relative to its parent) with the width and height utilities classes.

Width and height utilities are generated from the $sizes Sass map in Bootstrap's _variables.scss. Includes support for 25%, 50%, 75%, and 100% by default. Modify those values as you need to generate different utilities here.

Widths:

<div class="text-center">
  <div class="w-25 p-3 mb-1 bg-secondary">Width 25%</div>
  <div class="w-50 p-3 mb-1 bg-secondary">Width 50%</div>
  <div class="w-75 p-3 mb-1 bg-secondary">Width 75%</div>
  <div class="w-100 p-3 bg-secondary">Width 100%</div>
</div>

<!-- widths.vue -->

Heights:

<div style="height: 100px; background-color: rgba(255,0,0,0.1);">
  <div class="h-25 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">
    Height 25%
  </div>
  <div class="h-50 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">
    Height 50%
  </div>
  <div class="h-75 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">
    Height 75%
  </div>
  <div class="h-100 d-inline-block" style="width: 120px; background-color: rgba(0,0,255,.1)">
    Height 100%
  </div>
</div>

<!-- heights.vue -->

Max width and height:

You can also use mw-100 (max-width: 100%;) and mh-100 (max-height: 100%;) utilities as needed.

Additional resources

Refer to Bootstrap v4 official documentation site for more information.