Sass function and mixin to convert px in em.

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1902.0.0a year ago8 years agoMinified + gzip package size for sass-em in KB


Sass function and mixin to convert px in em.
Breaking change in 2.0: now using Sass Modules, using @use and em is renamed to em.convert. You could still use @import with no changes (see usage below), but if you need LibSass and Ruby Sass support (both deprecated), you should stay on 1.0 (which works fine) or use the PostCSS version.
Compatibility: Dart Sass only.
PostCSS version:
See also:


Install with Yarn or npm:
  • yarn add sass-em
  • npm install sass-em


The em.convert function takes at least 2 parameters: the value(s) (px, mixed) and the context (px). There can be multiple values (eg. multiple box shadow), but the last parameter must be the context.
The em.convert mixin takes only 2 parameters: the properties (map of property: value) and the context (px). It can be used to convert the values of multiple properties with the same context.
Import in your project depending of your setup:
@use "em";
// or @use "~sass-em" as em;
// or @use "../node_modules/sass-em" as em;

$base-font-size: 16px;
$h1-font-size: 24px;

.demo {
  font-size: em.convert($h1-font-size, $base-font-size); // Simple
  border-bottom: em.convert(1px solid black, $h1-font-size); // Shorthand
  box-shadow: em.convert(0 0 2px #ccc, inset 0 0 5px #eee, $h1-font-size); // Multiple values
  // Multiple properties
  @include em.convert((
    margin: 20px 5%,
    padding: 10px
  ), $h1-font-size);

Will output :
.demo {
  font-size: 1.5em;
  border-bottom: 0.0416666667em solid black;
  box-shadow: 0 0 0.0833333333em #ccc, inset 0 0 0.2083333333em #eee;
  margin: 0.8333333333em 5%;
  padding: 0.4166666667em;

But it was shorter before!

It was.
But You can change the namespace to something shorter and use em function and mixin instead of convert:
@use "em" as to; // Because why not?

.demo {
  font-size: to.em(24px, 16px);

Or you can even load the library globally (but beware of conflicts, avoided by the idea of modules):
@use "em" as *;

.demo {
  font-size: em(24px, 16px);

And if you just don't want to use Sass Modules, you can still use @import with em function and mixin as before:
@import "sass-em";

.demo {
  font-size: rem(24px);