sass-site/source/documentation/values/calculations.md

title	introduction
Calculations	Calculations are how Sass represents the `calc()` function, as well as similar functions like `clamp()`, `min()`, and `max()`. Sass will simplify these as much as possible, even if they're combined with one another.

{% compatibility 'dart: "1.40.0"', 'libsass: false', 'ruby: false' %} LibSass, Ruby Sass, and versions of Dart Sass prior to 1.40.0 parse calc() as a special function like element().

LibSass, Ruby Sass, and versions of Dart Sass prior to 1.31.0 parse clamp() as a plain CSS function rather than supporting special syntax within it. Versions of Dart Sass between 1.31.0 and 1.40.0 parse clamp() as a special function like element().

{% endcompatibility %}

{% codeExample 'calculations', false %} @debug calc(400px + 10%); // calc(400px + 10%) @debug calc(400px / 2); // 200px @debug min(100px, calc(1rem + 10%)); // min(100px, 1rem + 10%)

@debug calc(400px + 10%) // calc(400px + 10%) @debug calc(400px / 2) // 200px @debug min(100px, calc(1rem + 10%) ; // min(100px, 1rem + 10%) {% endcodeExample %}

Calculations use a special syntax that's different from normal SassScript. It's the same syntax as the CSS calc(), but with the additional ability to use Sass variables and call Sass functions. This means that / is always a division operator within a calculation!

{% funFact %} The arguments to a Sass function call use the normal Sass syntax, rather than the special calculation syntax! {% endfunFact %}

You can also use interpolation in a calculation. However, if you do, nothing in the parentheses that surround that interpolation will be simplified or type-checked, so it's easy to end up with extra verbose or even invalid CSS. Rather than writing calc(10px + #{$var}), just write calc(10px + $var)!

Simplification

Sass will simplify adjacent operations in calculations if they use units that can be combined at compile-time, such as 1in + 10px or 5s * 2. If possible, it'll even simplify the whole calculation to a single number—for example, clamp(0px, 30px, 20px) will return 20px.

{% headsUp %} This means that a calculation expression won't necessarily always return a calculation! If you're writing a Sass library, you can always use the meta.type-of() function to determine what type you're dealing with.

{% endheadsUp %}

Calculations will also be simplified within other calculations. In particular, if a calc() end up inside any other calculation, the function call will be removed and it'll be replaced by a plain old operation.

{% codeExample 'simplification' %} $width: calc(400px + 10%);

.sidebar { width: $width; padding-left: calc($width / 4); }

$width: calc(400px + 10%)

.sidebar width: $width padding-left: calc($width / 4) {% endcodeExample %}

Operations

You can't use calculations with normal SassScript operations like + and *. If you want to write some math functions that allow calculations just write them within their own calc() expressions—if they're passed a bunch of numbers with compatible units, they'll return plain numbers as well, and if they're passed calculations they'll return calculations.

This restriction is in place to make sure that if calculations aren't wanted, they throw an error as soon as possible. Calculations can't be used everywhere plain numbers can: they can't be injected into CSS identifiers (such as .item-#{$n}), for example, and they can't be passed to Sass's built-in math functions. Reserving SassScript operations for plain numbers makes it clear exactly where calculations are allowed and where they aren't.

{% codeExample 'calc-operations', false %} $width: calc(100% + 10px); @debug $width * 2; // Error! @debug calc($width * 2); // calc((100% + 10px) * 2);

$width: calc(100% + 10px); @debug $width * 2; // Error! @debug calc($width * 2); // calc((100% + 10px) * 2); {% endcodeExample %}

Constants

{% compatibility 'dart: "1.60.0"','libsass: false', 'ruby: false' %}{% endcompatibility %}

Calculations can also contain constants, which are written as CSS identifiers. For forwards-compatibility with future CSS specs, all identifiers are allowed, and by default they're just treated as unquoted strings that are passed-through as-is.

{% codeExample 'calc-constants', false %} @debug calc(h + 30deg); // calc(h + 30deg);

@debug calc(h + 30deg) // calc(h + 30deg); {% endcodeExample %}

Sass automatically resolves a few special constant names that are specified in CSS to unitless numbers:

• pi is a shorthand for the mathematical constant π.

• e is a shorthand for the mathematical constant e.

• infinity, -infinity, and NaN represent the corresponding floating-point values.

{% codeExample 'unitless-numbers', false %} @use 'sass:math';

@debug calc(pi); // 3.1415926536 @debug calc(e); // 2.7182818285 @debug calc(infinity) > math.$max-number; // true @debug calc(-infinity) < math.$min-number; // true

@use 'sass:math'

@debug calc(pi) // 3.1415926536 @debug calc(e) // 2.7182818285 @debug calc(infinity) > math.$max-number // true @debug calc(-infinity) < math.$min-number // true {% endcodeExample %}

min() and max()

{% compatibility 'dart: ">=1.11.0 <1.42.0"', 'libsass: false', 'ruby: false', 'feature: "Special function syntax"' %} LibSass, Ruby Sass, and versions of Dart Sass prior to 1.11.0 always parse min() and max() as Sass functions. To create a plain CSS min() or max() call for those implementations, you can write something like unquote("min(#{$padding}, env(safe-area-inset-left))") instead.

Versions of Dart Sass between 1.11.0 and 1.40.0, and between 1.40.1 and 1.42.0 parse min() and max() functions as special functions if they're valid plain CSS, but parse them as Sass functions if they contain Sass features other than interpolation, like variables or function calls.

Dart Sass 1.41.0 parses min() and max() functions as calculations, but doesn't allow unitless numbers to be combined with numbers with units. This was backwards-incompatible with the global min() and max() functions, so that behavior was reverted.

{% endcompatibility %}

CSS added support for min() and max() functions in Values and Units Level 4, from where they were quickly adopted by Safari to support the iPhoneX. But Sass supported its own min() and max() functions long before this, and it needed to be backwards-compatible with all those existing stylesheets. This led to the need for extra-special syntactic cleverness.

If a min() or max() function call is a valid calculation expression, it will be parsed as a calculation. But as soon as any part of the call contains a SassScript feature that isn't supported in a calculation, like the modulo operator, it's parsed as a call to Sass's core min() or max() function instead.

Since calculations are simplified to numbers when possible anyway, the only substantive difference is that the Sass functions only support units that can be combined at build time, so min(12px % 10, 10%) will throw an error.

{% headsUp %} Other calculations don't allow unitless numbers to be added to, subtracted from, or compared to numbers with units. min() and max() are different, though: for backwards-compatibility with the global Sass min() and max() functions which allow unit/unitless mixing for historical reasons, these units can be mixed as long as they're contained directly within a min() or max() calculation. {% endheadsUp %}

{% codeExample 'min-max' %} $padding: 12px;

.post { // Since these max() calls are valid calculation expressions, they're // parsed as calculations. padding-left: max($padding, env(safe-area-inset-left)); padding-right: max($padding, env(safe-area-inset-right)); }

.sidebar { // Since these use the SassScript-only modulo operator, they're parsed as // SassScript function calls. padding-left: max($padding % 10, 20px); padding-right: max($padding % 10, 20px); }

$padding: 12px

.post // Since these max() calls are valid calculation expressions, they're // parsed as calculations. padding-left: max($padding, env(safe-area-inset-left)) padding-right: max($padding, env(safe-area-inset-right))

.sidebar // Since these use the SassScript-only modulo operator, they're parsed as // SassScript function calls. padding-left: max($padding % 10, 20px) padding-right: max($padding % 10, 20px) {% endcodeExample %}