Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="Container">
  <div class="Container-left">
    left
  </div>
  <div class="Container-right">
    right
  </div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.4.9)
// Compass (v1.0.1)
// Susy (v2.1.3)
// ----

@import "susy";

$susy: (
  columns: 12
);

.Container {
  @include container; 
}

.Container-left {
  background-color: green;
  @include span(6);
}

.Container-right {
  background-color: blue;
  @include span(last 6);
}

SassMeister-output.css

.Container {
  max-width: 100%;
  margin-left: auto;
  margin-right: auto;
}
.Container:after {
  content: " ";
  display: block;
  clear: both;
}

.Container-left {
  background-color: green;
  width: 49.1525423729%;
  float: left;
  margin-right: 1.6949152542%;
}

.Container-right {
  background-color: blue;
  width: 49.1525423729%;
  float: right;
  margin-right: 0;
}

SassMeister-rendered.html

<div class="Container">
  <div class="Container-left">
    left
  </div>
  <div class="Container-right">
    right
  </div>
</div>