postcss-calc

What is postcss-calc?

The postcss-calc npm package is a PostCSS plugin that reduces CSS calc() function to the maximum, whenever it's possible. It simplifies calculations in CSS files and optimizes them during the build process, making the final CSS file lighter and easier for browsers to parse.

What are postcss-calc's main functionalities?

Simplification of calc expressions

This feature allows the simplification of calc expressions in CSS, reducing them to their simplest form. For example, if you have a calculation based on CSS custom properties or simple arithmetic, postcss-calc can compute these values at build time, resulting in cleaner and more efficient CSS.

css
.post {
  --gap: 20px;
  padding: calc(var(--gap) * 2);
}
/* becomes */
.post {
  padding: 40px;
}

Optimization of complex calculations

For more complex calculations that cannot be fully simplified without context (like viewport sizes or percentages), postcss-calc optimizes the expression to ensure it's as efficient as possible without altering the intended result.

css
.banner {
  width: calc(100% - 80px);
}
/* becomes */
.banner {
  width: calc(100% - 80px);
}

Other packages similar to postcss-calc

cssnano

cssnano is a modular CSS minifier that includes functionalities similar to postcss-calc as part of its optimizations. It uses PostCSS to analyze and rewrite CSS files, reducing their size. While cssnano includes a broader range of optimizations, postcss-calc focuses specifically on the optimization of calc() functions.

postcss-custom-properties

postcss-custom-properties is another PostCSS plugin that allows you to use CSS custom properties (variables) in your stylesheets. It can transform these properties into static values, similar to how postcss-calc simplifies calc() expressions. However, it focuses on variables rather than calculations.

README

PostCSS Calc

PostCSS Calc lets you reduce calc() references whenever it's possible. When multiple units are mixed together in the same expression, the calc() statement is left as is, to fallback to the W3C calc() implementation.

Installation

npm install postcss-calc

Usage

// dependencies
var fs = require("fs")
var postcss = require("postcss")
var calc = require("postcss-calc")

// css to be processed
var css = fs.readFileSync("input.css", "utf8")

// process css
var output = postcss()
  .use(calc())
  .process(css)
  .css

Using this input.css:

h1 {
  font-size: calc(16px * 2);
  height: calc(100px - 2em);
  width: calc(2*var(--base-width));
  margin-bottom: calc(16px * 1.5);
}

you will get:

h1 {
  font-size: 32px;
  height: calc(100px - 2em);
  width: calc(2*var(--base-width));
  margin-bottom: 24px
}

Checkout tests for more examples.

Options

precision (default: 5)

Allow you to define the precision for decimal numbers.

var out = postcss()
  .use(calc({precision: 10}))
  .process(css)
  .css

preserve (default: false)

Allow you to preserve calc() usage in output so browsers will handle decimal precision themselves.

var out = postcss()
  .use(calc({preserve: true}))
  .process(css)
  .css

warnWhenCannotResolve (default: false)

Adds warnings when calc() are not reduced to a single value.

var out = postcss()
  .use(calc({warnWhenCannotResolve: true}))
  .process(css)
  .css

mediaQueries (default: false)

Allows calc() usage as part of media query declarations.

var out = postcss()
  .use(calc({mediaQueries: true}))
  .process(css)
  .css

selectors (default: false)

Allows calc() usage as part of selectors.

var out = postcss()
  .use(calc({selectors: true}))
  .process(css)
  .css

Example:

div[data-size="calc(3*3)"] {
  width: 100px;
}

---

Related PostCSS plugins

To replace the value of CSS custom properties at build time, try PostCSS Custom Properties.

Contributing

Work on a branch, install dev-dependencies, respect coding style & run tests before submitting a bug fix or a feature.

git clone [e-mail]:postcss/postcss-calc.git
git checkout -b patch-1
npm install
npm test

Changelog

License