CSSGRID.net Convertido para SASS e com possibilidade de aumentar/diminuir a margem entre cada coluna do grid.

cssgrid.css.sass

$columns: 12
$margin: 1.8%

@function column-width($column)
  @return ($column * ((100% / $columns) - $margin)) + (($column - 1) * $margin)

.container
  padding-left: 20px
  padding-right: 20px

.row
  width: 100%
  max-width: 1140px
  min-width: 755px
  margin: 0 auto
  overflow: hidden

.onecol, .twocol, .threecol, .fourcol, .fivecol, .sixcol, .sevencol, .eightcol, .ninecol, .tencol, .elevencol
  margin-right: $margin
  float: left
  min-height: 1px

.row
  .onecol
    width: column-width(1) 
  .twocol
    width: column-width(2)
  .threecol
    width: column-width(3)
  .fourcol
    width: column-width(4)
  .fivecol
    width: column-width(5)
  .sixcol
    width: column-width(6)
  .sevencol
    width: column-width(7)
  .eightcol
    width: column-width(8)
  .ninecol
    width: column-width(9)
  .tencol
    width: column-width(10)
  .elevencol
    width: column-width(11)
  .twelvecol
    width: column-width(12)
    float: left

.last
  margin-right: 0px

img, object, embed
  max-width: 100%

img
  height: auto

/* Smaller screens

@media only screen and (max-width: 1023px)
  body
    font-size: 0.8em
    line-height: 1.5em

/* Mobile

@media handheld, only screen and (max-width: 767px)
  body
    font-size: 16px
    -webkit-text-size-adjust: none
  .row, body, .container
    width: 100%
    min-width: 0
    margin-left: 0px
    margin-right: 0px
    padding-left: 0px
    padding-right: 0px
  .row
    .onecol, .twocol, .threecol, .fourcol, .fivecol, .sixcol, .sevencol, .eightcol, .ninecol, .tencol, .elevencol, .twelvecol
      width: auto
      float: none
      margin-left: 0px
      margin-right: 0px
      padding-left: 20px
      padding-right: 20px