Generated by SassMeister.com.

SassMeister-input.scss

// ----
// Sass (v3.4.21)
// Compass (v1.0.3)
// ----

$font-size-base: 16px !default;
$view-width-base: 1024px !default;

@function _clean-unit($value) {
  @if type-of($value) == 'number' {
    @return $value / ($value * 0 + 1);
  } @else {
    @warn "#{$value} nao e um numero";
  }
}

@function _decimal-floor($number, $digits: 0) {
  $n: 1;
  $result: null;
  $number: _clean-unit($number);

  @if type-of($number) != number {
    @warn '#{$number} is not a number.';
    @return $result;
  }

  @if type-of($digits) != number {
    @warn '#{$digits} is not a number.';
    @return $result;
  }

  @if $digits > 0 {
    @for $i from 1 through $digits {
        $n: $n * 10;
    }
  }

  $result: floor($number * $n) / $n;

  @return $result;
}

@function vw($value) {
  @if type-of($value) == 'number' {
    $value: _clean-unit($value);
    $view-width: _clean-unit($view-width-base);
    
    $convertion: _decimal-floor(($value * 100) / $view-width, 2);

    @return $convertion * 1vw;
  } @else {
    @warn '#{$value} nao e um numero';
  }
}

.class {
  width: vw(300);
}

.class2 {
  width: vw(300px);
}

SassMeister-output.css

.class {
  width: 29.29vw;
}

.class2 {
  width: 29.29vw;
}