@function columns-width($num-columns) {
  $width: $num-columns * ($column-width + $gutter-width) - $gutter-width;
  @return max($width, 0);
}

@function units-width($num-units) {
  $width: $num-units * ($unit-width + $gutter-width) - $gutter-width;
  @return max($width, 0);
}