Generated by SassMeister.com.

SassMeister-input-HTML.html

<h1>This should be a responsive heading title right here</h1>

SassMeister-input.scss

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

@function strip-unit($number) {
  @if type-of($number) == 'number' and not unitless($number) {
    @return $number / ($number * 0 + 1);
  }

  @return $number;
}

@mixin responsive-text($min-font-size, $max-font-size, $min-screen-width, $max-screen-width) {
	font-size: calc(#{$min-font-size} + #{strip-unit($max-font-size - $min-font-size)} * ((100vw - #{$min-screen-width}) / #{strip-unit($max-screen-width - $min-screen-width)}));
}

h1 {
  @include responsive-text(20px, 60px, 600px, 1920px);
  font-family: sans-serif;
}

SassMeister-output.css

h1 {
  font-size: calc(20px + 40 * ((100vw - 600px) / 1320));
  font-family: sans-serif;
}

SassMeister-rendered.html

<h1>This should be a responsive heading title right here</h1>