Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="wrap">
  <div class="one item"></div>
  <div class="two item"></div>
  <div class="three item"></div>
  <div class="four item"></div>
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.14)
// Compass (v1.0.1)
// Susy (v2.1.3)
// ----

@import "susy";

$susy: (
  container: 960px,
  columns: 1 2 3 4 5, 
  column-width: 100px,
  gutters: 0.25,
  math: static, 
  output: isolate,
  global-box-sizing: border-box,
  gutter-position: after,
);

.wrap {
  @include container; 
}

.one {
  @include span(1 at 1);
}

.two {
  @include span(1 at 2);
}

.three {
  @include span(1 at 3);
}

.four {
  @include span(1 at 4);
}

.item {
  height: 60px;
  background: red;
  &:nth-child(2n) {
    background: blue;
  }
}

SassMeister-output.css

.wrap {
  width: 960px;
  margin-left: auto;
  margin-right: auto;
}
.wrap:after {
  content: " ";
  display: block;
  clear: both;
}

.one {
  width: 100px;
  float: left;
  margin-left: 0;
  margin-right: -100%;
}

.two {
  width: 200px;
  float: left;
  margin-left: 125px;
  margin-right: -100%;
}

.three {
  width: 300px;
  float: left;
  margin-left: 350px;
  margin-right: -100%;
}

.four {
  width: 400px;
  float: left;
  margin-left: 675px;
  margin-right: -100%;
}

.item {
  height: 60px;
  background: red;
}
.item:nth-child(2n) {
  background: blue;
}

SassMeister-rendered.html

<div class="wrap">
  <div class="one item"></div>
  <div class="two item"></div>
  <div class="three item"></div>
  <div class="four item"></div>
</div>