Modular scale stepper function, for moving up and down a modular scale.

_ms.scss

/**!
 * SCSS Modular scale function
 * Will use $ms-base as the scale, and $degrees to calculate stops on the scale
 *
 * @author Jason Howmans <@jhwmns>
 *
 * @examples
 * Usage example for font size:
 *   // Using a scale of 1.4, this will output font-size: 1.96rem;
 *   font-size: #{ms(2)}rem;
 *
 * Will also work with backward steps
 *   // Using a scale of 1.4, this will output font-size: .714rem;
 *   font-size: #{ms(-1)}rem;
 */

 $ms-base: 1.4;

 @function ms($degrees:1) {
   $num: 1;
   $isNegative: false;
   @if $degrees < 0 {
     $isNegative: true;
     $degrees: $degrees * -1;
   }
   @for $i from 1 through $degrees {
     @if $isNegative {
       $num: $num / $ms-base;
     } @else {
       $num: $num * $ms-base;
     }
   }
   @return round($num * 1000) / 1000; // round to three decimal places
 }