/* UNIT OPTIONS */
$min: 0;
$max: 25;
$rem-factor: 0.25;

@function unit-to-rem($unit) {
  @if $unit >= $min and $unit <= $max {
    @return calc($unit * $rem-factor) + rem;
  } @else {
    @error "Value #{$unit} is invalid. Unit must be from #{$min} to #{$max}.";
  }
}