sass-site/source/documentation/at-rules/control/while.liquid

---
title: "@while"
introduction: >
  The `@while` rule, written `@while <expression> { ... }`, evaluates its block
  if its [expression](/documentation/syntax/structure#expressions) returns
  `true`. Then, if its expression still returns `true`, it evaluates its block
  again. This continues until the expression finally returns `false`.
---

{% codeExample 'while' %}
@use "sass:math";

/// Divides `$value` by `$ratio` until it's below `$base`.
@function scale-below($value, $base, $ratio: 1.618) {
  @while $value > $base {
    $value: math.div($value, $ratio);
  }
  @return $value;
}

$normal-font-size: 16px;
sup {
  font-size: scale-below(20px, 16px);
}
===
@use "sass:math"

/// Divides `$value` by `$ratio` until it's below `$base`.
@function scale-below($value, $base, $ratio: 1.618)
  @while $value > $base
    $value: math.div($value, $ratio)
  @return $value



$normal-font-size: 16px
sup
  font-size: scale-below(20px, 16px)
===
sup {
  font-size: 12.36094px;
}
{% endcodeExample %}

{% headsUp %}
Although `@while` is necessary for a few particularly complex stylesheets,
you're usually better of using either [`@each`][] or [`@for`][] if either of
them will work. They're clearer for the reader, and often faster to compile as
well.

[`@each`]: /documentation/at-rules/control/each
[`@for`]: /documentation/at-rules/control/for
{% endheadsUp %}

{% render 'documentation/snippets/truthiness-and-falsiness' %}