PostCSS px To em

PostCSS plugin to convert all px measurements to em.

.foo {
  width: 270px;
  margin: 0 15px;
  padding: 1em;
 
  /* you can override pixel replacement by adding a "force" *
   * comment after the pixel measurement you want to keep.  */
  border-radius: 10px /*force*/ 16px;
}
 
@media (min-width: 640px) {
  /* doesn't change pixel values used for media queries, as this wouldn't work properly */
  .foo {
    width: 100%;
    padding: 10px;
  }
}

.foo {
  width: 16.875em;
  margin: 0 0.9375em;
  padding: 1em;
 
  /* you can override pixel replacement by adding a "force" *
   * comment after the pixel measurement you want to keep.  */
  border-radius: 10px /*force*/ 1em;
}
 
@media (min-width: 640px) {
  /* doesn't change pixel values used for media queries, as this wouldn't work properly */
  .foo {
    width: 100%;
    padding: 0.625em;
  }
}

Rationale

For Bugherd, we needed to be able to scale our UIs to fit any zoom level on Mobile. To enable this, we change the parents' font-size and use em measurements relative to the base font size (usually 16px) in our components. This PostCSS plugin facilitates this, without requiring us to rewrite all our code to use em manually.

Usage

Plug it into your PostCSS configuration.

var options = {
  base: 16, // Base font size; 16px by default
};
 
// Options may be supplied as the first argument, but are not required.
postcss([require('postcss-px-to-em')(options)])

See PostCSS docs for examples for your environment.