Generated by SassMeister.com.

SassMeister-input.scss

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

/* _settings.scss */
$blue: blue;
$black: black;

/* původní komponenta */
@mixin unread-mark($background) {
	width: 50px;
	height: 50px;
	background: $background;
	border-radius: 50px; // zde nemusíš používat rem-calc

	// For custom content
	@content;
}

.unread-mark {
	@include unread-mark($blue);
}

.navbar {
	@include unread-mark($black) {
		width: 80px;
		height: 80px;
	}
}

SassMeister-output.css

@charset "UTF-8";
/* _settings.scss */
/* původní komponenta */
.unread-mark {
  width: 50px;
  height: 50px;
  background: blue;
  border-radius: 50px;
}

.navbar {
  width: 50px;
  height: 50px;
  background: black;
  border-radius: 50px;
  width: 80px;
  height: 80px;
}