Really small and Simple Sass Grid system

pinky.scss

[class*='col-'] {
  //Aligns the columns next to each other
    width: 100%;
    float:left;
    min-height: 1px;
}
// an extend only class for clearfixing
%clearfix {
    *zoom: 1;
    &:before, 
    &:after { content: " "; display: table;}
    &:after { clear: both;}
}
//simple container add media queries if you need them.
.container {
    width:1140px;
    margin:0 auto;
   @extend %clearfix;
}

@mixin col($col, $sum) {
  //mixin for naming convention and column maths
  width: percentage($col/$sum);
  display: inline-block;
  @media only screen and (max-width: 768px) {
    // change this or add more for each screen size
   width: 100%;
  }
}

//Loop through all columns 
$col_num: 12;
@for $i from 1 through $col_num {
    $name: xs;
    .col-#{$name}-#{$i}{ @include col($i, $col_num);}
    $name: sm;
    .col-#{$name}-#{$i}{ @include col($i, $col_num);}
    $name: md;
    .col-#{$name}-#{$i}{ @include col($i, $col_num);}
    $name: lg;
    .col-#{$name}-#{$i}{ @include col($i, $col_num);}
}