Rounding decimals in Sass

_decimal.scss

// _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);
}

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!

I love your logic!

Thank you.

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

Thank you, great!

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;
    }
}

nice job

awesome logic @Terke.

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?

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