Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="wrap">
  <div class="sidebar">Sidebar</div>
  <div class="content">Content</div>
</div>

SassMeister-input.scss

// ----
// libsass (v3.2.4)
// ----

@import "susy";

$susy: (
  columns: 12,
  container: 1120px,
  global-box-sizing: border-box 
);
@include border-box-sizing;

.wrap {
  @include container;  
}

.sidebar {
  @include span(3); 
  border: solid 1px #D9D9D9;
  height: 200px;
}

.content {
  @include span(9 last); 
  border: solid 1px #D9D9D9;
  height: 200px;
}

SassMeister-output.css

*, *:before, *:after {
  -moz-box-sizing: border-box;
  -webkit-box-sizing: border-box;
  box-sizing: border-box;
}

.wrap {
  max-width: 1120px;
  margin-left: auto;
  margin-right: auto;
}

.wrap:after {
  content: " ";
  display: block;
  clear: both;
}

.sidebar {
  width: 23.72881%;
  float: left;
  margin-right: 1.69492%;
  border: solid 1px #D9D9D9;
  height: 200px;
}

.content {
  width: 74.57627%;
  float: right;
  margin-right: 0;
  border: solid 1px #D9D9D9;
  height: 200px;
}

SassMeister-rendered.html

<div class="wrap">
  <div class="sidebar">Sidebar</div>
  <div class="content">Content</div>
</div>