Generated by SassMeister.com.

SassMeister-input.scss

// ----
// libsass (v3.1.0)
// ----

$default-font-size: 16;

@function remove-unit($num) {
  @return $num / ($num * 0 + 1);
}
@mixin rem($property, $values) {
  $total: length($values);
  $px-value: "";
  $rem-value: "";
  
  @for $i from 1 through $total {
    $value: nth($values, $i);
    
    // Check if $value is string or not
    @if type_of($value) != string{
      // convert to REM
      $value: remove-unit(nth($values, $i));
      $px-value: #{$px-value + $value}px;
      $rem-value: #{$rem-value + $value / $default-font-size}rem;
    }
    @else {
      // pass value is string
      $value: nth($values, $i);
      $px-value: #{$px-value + $value};
      $rem-value: #{$rem-value + $value};
    }
    
    @if $i < $total {
      // Set PX
      $rem-value: #{$rem-value + " "};
      // Set REM
      $px-value: #{$px-value + " "};
    }
  }
  #{$property}: $px-value;
  #{$property}: $rem-value;
}

/* WITH VALUES */
@include rem(padding, 12px 16px);
@include rem(margin, 16 20);

/* WITH AUTO */
@include rem(margin, 12px auto);
@include rem(margin, 16 auto);

SassMeister-output.css

/* WITH VALUES */
padding: 12px 16px;
padding: 0.75rem 1rem;
margin: 16px 20px;
margin: 1rem 1.25rem;
/* WITH AUTO */
margin: 12px auto;
margin: 0.75rem auto;
margin: 16px auto;
margin: 1rem auto;