Sass mixin for setting an element's size.

size.scss

// Size mixin.
// https://gist.github.com/brianmcallister/3659524
// 
// $width  - Element width, with units.
// $height - Optional height of the element. Expects units, ex: 5px.
//           Defaults to null.
@mixin size($width, $height: null) {
  width: $width;
  
  @if $height {
    height: $height;
  } @else {
    height: $width;
  }
}