Aspect Ratio

Utilities for controlling the aspect ratio of an element.

Use the ratio helper to manage the aspect ratios of external content like <iframe>s, <embed>s, <video>s, and <object>s. These helpers also can be used on any standard HTML child element (e.g., a <div> or <img>). Styles are applied from the parent .ratio class directly to the child.

Quick reference

.ratio-1x1aspect-ratio: 1 / 1;
.ratio-4x3aspect-ratio: 3 / 4;
.ratio-16x9aspect-ratio: 9 / 16;
.ratio-21x9aspect-ratio: 9 / 21;

Basic usage

Embed YouTube video

Wrap any embed, like an <iframe>, in a parent element with .ratio and an aspect ratio class. The immediate child element is automatically sized thanks to our universal selector .ratio > *.

<div class="ratio ratio-16x9">
    title="YouTube video"

Keep image aspect ratio

Use the radio-* as a media container and put an image with .img-fluid as a child element.

4 : 3
16 : 9
<div class="ratio ratio-4x3">
  <img class="img-fluid" src="path/to/image.jpg" />

Custom ratios

Each .ratio-* class includes a CSS custom property (or CSS variable) in the selector. You can override this CSS variable to create custom aspect ratios on the fly with some quick math on your part.

For example, to create a 2x1 aspect ratio, set --bs-aspect-ratio: 50% on the .ratio.

<div class="ratio" style="--bs-aspect-ratio: 50%;">

This CSS variable makes it easy to modify the aspect ratio across breakpoints. The following is 4x3 to start, but changes to a custom 2x1 at the medium breakpoint.

.ratio-4x3 {
  @include media-breakpoint-up(md) {
    --bs-aspect-ratio: 50%; // 2x1