About
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.
Aspect ratios are declared in a Sass map and included in each class via CSS variable, which also allows custom aspect ratios.
Example
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 > *.
Aspect ratios
Aspect ratios can be customized with modifier classes. By default the following ratio classes are provided:
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.
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
}
}
Sass map
Within _variables.scss, you can change the aspect ratios you want to use. Here’s our default $ratio-aspect-ratios map. Modify the map as you like and recompile your Sass to put them to use.
$aspect-ratios: (
"1x1": 100%,
"4x3": calc(3 / 4 * 100%),
"16x9": calc(9 / 16 * 100%),
"21x9": calc(9 / 21 * 100%)
);