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@terkel
Last active June 17, 2024 14:07
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Rounding decimals in Sass
// _decimal.scss | MIT License | gist.github.com/terkel/4373420
// Round a number to specified digits.
//
// @param {Number} $number A number to round
// @param {Number} [$digits:0] Digits to output
// @param {String} [$mode:round] (round|ceil|floor) How to round a number
// @return {Number} A rounded number
// @example
// decimal-round(0.333) => 0
// decimal-round(0.333, 1) => 0.3
// decimal-round(0.333, 2) => 0.33
// decimal-round(0.666) => 1
// decimal-round(0.666, 1) => 0.7
// decimal-round(0.666, 2) => 0.67
//
@function decimal-round ($number, $digits: 0, $mode: round) {
$n: 1;
// $number must be a number
@if type-of($number) != number {
@warn '#{ $number } is not a number.';
@return $number;
}
// $digits must be a unitless number
@if type-of($digits) != number {
@warn '#{ $digits } is not a number.';
@return $number;
} @else if not unitless($digits) {
@warn '#{ $digits } has a unit.';
@return $number;
}
@for $i from 1 through $digits {
$n: $n * 10;
}
@if $mode == round {
@return round($number * $n) / $n;
} @else if $mode == ceil {
@return ceil($number * $n) / $n;
} @else if $mode == floor {
@return floor($number * $n) / $n;
} @else {
@warn '#{ $mode } is undefined keyword.';
@return $number;
}
}
// Ceil a number to specified digits.
//
// @param {Number} $number A number to round
// @param {Number} [$digits:0] Digits to output
// @return {Number} A ceiled number
// @example
// decimal-ceil(0.333) => 1
// decimal-ceil(0.333, 1) => 0.4
// decimal-ceil(0.333, 2) => 0.34
// decimal-ceil(0.666) => 1
// decimal-ceil(0.666, 1) => 0.7
// decimal-ceil(0.666, 2) => 0.67
//
@function decimal-ceil ($number, $digits: 0) {
@return decimal-round($number, $digits, ceil);
}
// Floor a number to specified digits.
//
// @param {Number} $number A number to round
// @param {Number} [$digits:0] Digits to output
// @return {Number} A floored number
// @example
// decimal-floor(0.333) => 0
// decimal-floor(0.333, 1) => 0.3
// decimal-floor(0.333, 2) => 0.33
// decimal-floor(0.666) => 0
// decimal-floor(0.666, 1) => 0.6
// decimal-floor(0.666, 2) => 0.66
//
@function decimal-floor ($number, $digits: 0) {
@return decimal-round($number, $digits, floor);
}
@zachhanding
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Needed a way to floor percentages to specified decimal places instead of just down to the whole number, and this did exactly that for me. Thanks!

@PurpleBracket
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I love your logic!

@stevenvachon
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Thank you.

@iRouge
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iRouge commented Mar 11, 2016

Thank you, I was about to build one for myself. Your saving me time.

@thomasfrobieter
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Thank you, great!

@jslegers
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jslegers commented Oct 7, 2016

If you want 0 digits, it rounds to 2 digits instead.

Here's a fix :

@function decimal-round ($number, $digits: 0, $mode: round) {
    $n: 1;
    // $number must be a number
    @if type-of($number) != number {
        @warn '#{ $number } is not a number.';
        @return $number;
    }
    // $digits must be a unitless number
    @if type-of($digits) != number {
        @warn '#{ $digits } is not a number.';
        @return $number;
    } @else if not unitless($digits) {
        @warn '#{ $digits } has a unit.';
        @return $number;
    }
    @if $digits > 0 {
        @for $i from 1 through $digits {
            $n: $n * 10;
        }
    }
    @if $mode == round {
        @return round($number * $n) / $n;
    } @else if $mode == ceil {
        @return ceil($number * $n) / $n;
    } @else if $mode == floor {
        @return floor($number * $n) / $n;
    } @else {
        @warn '#{ $mode } is undefined keyword.';
        @return $number;
    }
}

@cmevawala
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nice job

@Subhojit1992
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awesome logic @Terke.

@SassNinja
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Good catch @jslegers!

Your condition is needed

@if $digits > 0 {
    @for $i from 1 through $digits {
        $n: $n * 10;
    }
}

because without it @include decimal-round(1.666, 0) returns 1.67 instead of 2.

@terkel would you mind to update the code?

@gladchinda
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Great implementation @terkel!

Here is a more concise implementation that I use in my own projects:

@function pow ($value, $pow: 1) {
  @return if($pow == 0, 1, $value * pow($value, $pow - 1));
}

@function rounded ($value, $precision: 1) {
  $pow10: pow(10, $precision);
  @return round($value * $pow10) / $pow10;
}

:root {
  --round-width: #{round(200% / 3)};          // 67%
  --rounded-width: #{rounded(200% / 3, 6)};   // 66.666667%
}
  • it relies on a pow() function,
  • it handles units as well

@greycode-007
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this is so cool. thanks terkel

@sujaykumarh
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dart-sass deprecating use of / for division

fix:

// import at top of file
@use "sass:math";

Replacements

@return round($number * $n) / $n;

with

@return math.div(math.round($number * $n), $n);

@return ceil($number * $n) / $n;

with

@return math.div(math.ceil($number * $n), $n);

@return floor($number * $n) / $n;

with

@return math.div(math.floor($number * $n), $n);

@mtsweir
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mtsweir commented Jul 14, 2022

Is there a way to round decimal points in this example?

//
// Aspect ratio
//
// Example:
//
// 16:9 aspect ratio, use:
//
// .element {
// 	@include aspectRatio(16, 9);
// }
//
// 4:3 aspect ratio, use:
//
// .element {
// 	@include aspectRatio(4, 3);
// }
//

@use "sass:math";

@mixin aspectRatio($width, $height) {
	position: relative;

	&:before {
		display: block;
		content: "";
		padding-top: math.div($height, $width) * 100%;
		width: 100%;
	}

	> * {
		position: absolute;
		top: 0;
		bottom: 0;
		left: 0;
		width: 100%;
		height: 100%;
		border: 0;
	}
}

For a 16/9 aspect ratio, I am getting 56.25% - would be nice to round that down to 56% if possible.

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