// Base font size in pixels
$base-font-size: 16;

// Convert pixels to em
@function pem($px, $base: $base-font-size) {

  @if (unitless($px)) {
    $px: $px * 1px;
  }

  @if (unitless($base)) {
    $base: $base * 1px;
  }

  @return $px / $base * 1em;
}