Sass mixins to convert px to em

px to em(sass)

$base: 15;

@function em($pixels, $context: $base) {
    @if (unitless($pixels)) {
        $pixels: $pixels * 1px;
    }

    @if (unitless($context)) {
        $context: $context * 1px;
    }

    @return $pixels / $context * 1em;
}

//Usage
h1{ 
    font-size: em(15);
    //returns 0.9375rem
}