Sass math.is-unitless()

Definition and Usage

math.is-unitless($number) returns whether $number has no units. It is a boolean check only — it does not strip units. Load it with @use "sass:math" (Dart Sass 1.23+ for modules).

Syntax

@use "sass:math";

math.is-unitless($number); //=> boolean

math.is-unitless(100);   // true
math.is-unitless(100px); // false

// Global name (legacy / deprecated in modern Dart Sass)
unitless(100); // true

// Module API — prefer math.is-unitless after @use "sass:math"

Pattern: inspect a token → branch with @if → only then call helpers that require unitless input (math.log, math.pow, math.sqrt). Inspect the unit string with math.unit.

What Counts as Unitless

Verified results for common numbers:

Related Functions

Load with @use "sass:math". Previous: math.hypot(). Next: math.log(). Also: math.unit(), math.compatible(), math.div(), math.percentage(), @if.

SCSS Examples

Examples target Dart Sass with @use "sass:math". Open View Compiled CSS for verified output (matches official Sass docs samples).

@use "sass:math";

@debug math.is-unitless(100); // true

.basic {
  --a: #{math.is-unitless(100)};
}

.basic {
  --a: true;
}

@use "sass:math";

@debug math.is-unitless(100px); // false

.units {
  --b: #{math.is-unitless(100px)};
}

.units {
  --b: false;
}

@use "sass:math";

.kinds {
  --pct: #{math.is-unitless(50%)};
  --rem: #{math.is-unitless(1.5rem)};
  --zero: #{math.is-unitless(0)};
}

.kinds {
  --pct: false;
  --rem: false;
  --zero: true;
}

@use "sass:math";

$px: 18px;
$bare: math.div($px, 1px);

.strip {
  --before: #{math.is-unitless($px)};
  --after: #{math.is-unitless($bare)};
  --value: #{$bare};
}

.strip {
  --before: false;
  --after: true;
  --value: 18;
}

@use "sass:math";

$n: 1.25;

.gate {
  @if math.is-unitless($n) {
    opacity: $n;
  } @else {
    opacity: 1;
  }
}

.gate {
  opacity: 1.25;
}

Sass Support

Prefer the module form with Dart Sass 1.23+.

Compile with the Dart Sass CLI.

Key Takeaways

Compile Notes

Practical checklist:

1. @use "sass:math"
2. Call math.is-unitless($number)
3. true → safe for log/pow/sqrt/acos-style helpers
4. false → cancel units with math.div or branch with @if
5. Prefer math.is-unitless over global unitless()