_functions.scss

// Strip the unit from the given value and return the value
@function strip-unit($value) {
    @return $value / ($value * 0 + 1);
}

// Return an em unit based on the pixel value and context
@function rem($px, $context: $base-font-size) {
    @return #{strip-unit($px / strip-unit($context))}rem;
}