Sass mixin to convert a ratio to a percentage.

_ratio-as-percentage.scss

// Convert a ratio into a percentage. Useful for responsive images and videos.
// https://gist.github.com/brianmcallister/03b9038b45c02dabba3a779efc6c4e38
//
// $ratio - 2 item list of integers. Represents a ratio. Defaults to 1:1.
//
// Examples
//
//   ratio-as-percentage();
//   #=> 100%
//
//   ratio-as-percentage(16 9);
//   #=> 56.25%
//
// Returns a percent value.
@function ratio-as-percentage($ratio: 1 1) {
  @if length($ratio) < 2 or length($ratio) > 2 {
    @warn '$ratio must be a list with two values.';
  }

  @return percentage(nth($ratio, 2) / nth($ratio, 1));
}