content-width.css

#wrap {
  width: 940px;
}

#content {
  width: 520px;
  padding-right: 60px;
  padding-left: 60px;
  margin-right: 60px;
  margin-left: 60px;
}

#sidebar {
  width: 74px;
  margin-right: 76px;
}

.nav {
  width: 820px;
  margin-left: -410px;
}

content-width.scss

$content-width: 640px;
$wrap-width: $content-width + 300;
$content-padding: 60px;
$sidebar-width: 74px;
$nav-width: $content-width + 180px;

#wrap {
  width: $wrap-width;
}

#content {
  width: $content-width - (2 * $content-padding);
  padding-right: $content-padding;
  padding-left: $content-padding;
  margin-right: 60px;
  margin-left: 60px;
}

#sidebar {
  width: $sidebar-width;
  margin-right: ($wrap-width - $content-width) / 2 - $sidebar-width;
}

.nav {
  width: $nav-width;
  margin-left: $nav-width / 2 * -1;
}