Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.6)
// Compass (v1.0.1)
// ----

@function grid-width($count, $gutter, $width){
 $grid-width: ($count - 1) * $gutter + ($count * $width);
 @return $grid-width;
}

@function context-width($context, $width, $gutter) {
  $context-width: $context * ($width + $gutter); 
   @return $context-width;
}

@mixin the-grid($count, $context: 12, $width: 60, $gutter: 20) {
  $grid-width:grid-width($count, $gutter, $width);
  $context-width:context-width($context, $width, $gutter);
 width: percentage($grid-width / $context-width);
}

.block {
  @include the-grid(6);
}

SassMeister-output.css

.block {
  width: 47.91667%;
}