960gs in SCSS mixin

grid.scss

$page_width: 850px;

@function grid_width($width, $margin, $columns) { 
  @return ($width - ($margin * ($columns - 1))) / $columns;
}

@mixin grid-column($columns, $prefix, $sufix, $gutter, $border_right, $border_left, $cw, $cm) {
  $width: (($cw + $cm) * $columns) - $cm;
  $prefix_width: ($cw + $cm) * $prefix;
  $sufix_width: ($cw + $cm) * $sufix;
  @if $gutter {
    $sufix_width: $sufix_width + $cm;
  }
  display: inline-block;
  margin-left: $prefix_width;
  margin-right: $sufix_width;
  width: $width - $border_left - $border_right;
  vertical-align: top;
  &:last-child {
    margin-right: 0;
  }
}

// (850-15*4)/5 = 158
@mixin grid-columnx5($columns: 1, $prefix: 0, $sufix: 0, $gutter: true, $border_right: 0, $border_left: 0) {
  $cm: 15px;
  $cw: grid_width($page_width, $cm, 5);
  @include grid-column($columns, $prefix, $sufix, $gutter, $border_right, $border_left, $cw, $cm);
}

//(850-35*2)/3 = 260
@mixin grid-columnx3($columns: 1, $prefix: 0, $sufix: 0, $gutter: true, $border_right: 0, $border_left: 0) {
  $cm: 20px;
  $cw: grid_width($page_width, $cm, 3);
  @include grid-column($columns, $prefix, $sufix, $gutter, $border_right, $border_left, $cw, $cm);
}

.columnx5-1 {
  @include grid-columnx5(1);
}
.columnx5-2 {
  @include grid-columnx5(2);
}
.columnx5-4 {
  @include grid-columnx5(4);
}