Generated by SassMeister.com.

SassMeister-input-HTML.html

<div>
  
</div>

SassMeister-input.scss

// ----
// Sass (v3.3.0.rc.5)
// Compass (v1.0.0.alpha.18)
// ----

@mixin dbl-border($color) {
  background: $color;
  position: relative;
  
  &:before {
    border: 1px solid $color;
    content: '';
    height: 101%;
    height: calc(100% + 10px);
    left: -5px;
    position: absolute;
    top: -5px;
    width: 101%;
    width: calc(100% + 10px);
  }
}

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


div {
  height: 400px;
  width: 500px;
  @include dbl-border(red);
}

SassMeister-output.css

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

div {
  height: 400px;
  width: 500px;
  background: red;
  position: relative;
}
div:before {
  border: 1px solid red;
  content: '';
  height: 101%;
  height: calc(100% + 10px);
  left: -5px;
  position: absolute;
  top: -5px;
  width: 101%;
  width: calc(100% + 10px);
}

SassMeister-rendered.html

<div>
  
</div>