Generated by SassMeister.com.

SassMeister-input-HTML.html

<div class="header">
  <div class="logo">Logo</div>
</div>
<div class="sidebar">
  Sidebar
</div>

SassMeister-input.scss

// ----
// libsass (v3.2.5)
// ----

.logo {
  background-color: blue;
  width: 50px;
  height: 50px;
  line-height: 50px;
  color: #fff;
  text-align: center;
}

.sidebar {
  background-color: #333;
  color: #fff;  
  float: right;
  min-height: 400px;
  padding: 30px;
  
  width: calc(100% - 110px); /* 50px logo + 60px padding = 110px */

}

SassMeister-output.css

.logo {
  background-color: blue;
  width: 50px;
  height: 50px;
  line-height: 50px;
  color: #fff;
  text-align: center;
}

.sidebar {
  background-color: #333;
  color: #fff;
  float: right;
  min-height: 400px;
  padding: 30px;
  width: calc(100% - 110px);
  /* 50px logo + 60px padding = 110px */
}

SassMeister-rendered.html

<div class="header">
  <div class="logo">Logo</div>
</div>
<div class="sidebar">
  Sidebar
</div>