$base-font-size: 16;

@function strip-unit($number) {
  @if type-of($number) == 'number' and not unitless($number) {
    @return $number / ($number * 0 + 1);
  }
  @return $number;
}

@function px-to-rem($size, $base: $base-font-size) {
  $pxUnitless: strip-unit($size);
  @return #{calc($pxUnitless / $base)}rem;
}