Generated by SassMeister.com.

SassMeister-input.scss

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

$max-width: 1100px;
$margin: 15px;
$margin-p: percentage(15px / 1100px);

$grid: (
  one-col: 1100px - $margin,
  two-col: 550px - $margin
);

@function columns($key) {
  @if map-has-key($grid, $key) {
    @return map-get($grid, $key);
  }
}

@function calc-em($target-px, $context) {
  @return ($target-px / $context) * 1em;
}

@mixin grid($args1, $args2) {
  width: percentage(columns($args1) / $max-width);
  margin-right: $args2;
} 

div {
  @include grid(one-col, 15px);
}

SassMeister-output.css

div {
  width: 98.63636%;
  margin-right: 15px;
}