$grid-gutter: 16px;
$grid-columns: 12;
$grid-max: 1004px;

[class*="grid-"]{
  float: left;
  padding: 0 $grid-gutter;
  margin-bottom: 20px;
  box-sizing: border-box;
}

@for $i from 1 through $grid-columns{
  .grid-#{$i}{
    width: 100% / $grid-columns * $i
  }
}