Sass math.round()

Definition and Usage

math.round($number) rounds $number to the nearest whole number. Whole numbers stay the same. Units such as px are kept. Load it with @use "sass:math" (Dart Sass 1.23+ for modules; global round() also exists).

Syntax

@use "sass:math";

math.round($number); //=> number (units preserved)

math.round(4);    // 4
math.round(4.2);  // 4
math.round(4.9);  // 5
math.round(4.5px); // 5px

// Global name (legacy / deprecated in modern Dart Sass)
round(4.9); // 5

// Module API — prefer math.round after @use "sass:math"

Pattern: compute a fractional length or count → math.round for the nearest whole value → use math.floor or math.ceil when the rounding direction must be forced.

Units and Halves

Nearest whole number, with units preserved:

Related Functions

Load with @use "sass:math". Previous: math.random(). Next: math.sin(). Also: math.ceil(), math.floor(), math.abs(), math.clamp(), math.percentage().

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.round(4);   // 4
@debug math.round(4.2); // 4
@debug math.round(4.9); // 5

.basic {
  --a: #{math.round(4)};
  --b: #{math.round(4.2)};
  --c: #{math.round(4.9)};
}

.basic {
  --a: 4;
  --b: 4;
  --c: 5;
}

@use "sass:math";

.units {
  --px: #{math.round(4.5px)};
  --neg: #{math.round(-4.2)};
  --neg2: #{math.round(-4.6)};
}

.units {
  --px: 5px;
  --neg: -4;
  --neg2: -5;
}

@use "sass:math";

.half {
  --h: #{math.round(4.5)};
}

.half {
  --h: 5;
}

@use "sass:math";

.compare {
  --ceil: #{math.ceil(4.2)};
  --floor: #{math.floor(4.2)};
  --round: #{math.round(4.2)};
}

.compare {
  --ceil: 5;
  --floor: 4;
  --round: 4;
}

@use "sass:math";

$w: 12.4px;

.box {
  width: math.round($w);
}

.box {
  width: 12px;
}

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. Pass a number (units optional)
3. Expect the nearest whole value
4. Prefer math.round over global round()
5. Use floor/ceil when the direction must be forced