Most mobile and cross-platform web developers have encountered the problem at some point: you need your web app to scale neatly to the device screen size, regardless of which of the many thousands of devices there are out there, but your units only have one design layout width, mainly mobile.

Grappling with this problem in one of our projects our leading frontend developer Dmitriy Karpunin came up with the idea of using a post-processor to convert CSS values from one set of units to another, and that’s how postcss-px-to-viewport, a plug-in for PostCSS that converts px values to viewport units (vw, vh, etc.), was born.

Programming language: JavaScript
License: MIT License
Tags: Worth Reading     Css     frontend     PostCSS    
Latest version: v1.1.1

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NPM version

English | [中文](README_CN.md)

A plugin for PostCSS that generates viewport units (vw, vh, vmin, vmax) from pixel units.


If your project involves a fixed width, this script will help to convert pixels into viewport units.


.class {
  margin: -10px .5vh;
  padding: 5vmin 9.5px 1px;
  border: 3px solid black;
  border-bottom-width: 1px;
  font-size: 14px;
  line-height: 20px;

.class2 {
  padding-top: 10px; /* px-to-viewport-ignore */
  /* px-to-viewport-ignore-next */
  padding-bottom: 10px;
  /* Any other comment */
  border: 1px solid black;
  margin-bottom: 1px;
  font-size: 20px;
  line-height: 30px;

@media (min-width: 750px) {
  .class3 {
    font-size: 16px;
    line-height: 22px;


.class {
  margin: -3.125vw .5vh;
  padding: 5vmin 2.96875vw 1px;
  border: 0.9375vw solid black;
  border-bottom-width: 1px;
  font-size: 4.375vw;
  line-height: 6.25vw;

.class2 {
  padding-top: 10px;
  padding-bottom: 10px;
  /* Any other comment */
  border: 1px solid black;
  margin-bottom: 1px;
  font-size: 6.25vw;
  line-height: 9.375vw;

@media (min-width: 750px) {
  .class3 {
    font-size: 16px;
    line-height: 22px;

Getting Started


Add via npm

$ npm install postcss-px-to-viewport --save-dev

or yarn

$ yarn add -D postcss-px-to-viewport


Default Options:

  unitToConvert: 'px',
  viewportWidth: 320,
  unitPrecision: 5,
  propList: ['*'],
  viewportUnit: 'vw',
  fontViewportUnit: 'vw',
  selectorBlackList: [],
  minPixelValue: 1,
  mediaQuery: false,
  replace: true,
  exclude: undefined,
  include: undefined,
  landscape: false,
  landscapeUnit: 'vw',
  landscapeWidth: 568
  • unitToConvert (String) unit to convert, by default, it is px.
  • viewportWidth (Number) The width of the viewport.
  • unitPrecision (Number) The decimal numbers to allow the vw units to grow to.
  • propList (Array) The properties that can change from px to vw.
    • Values need to be exact matches.
    • Use wildcard * to enable all properties. Example: ['*']
    • Use * at the start or end of a word. (['position'] will match background-position-y)
    • Use ! to not match a property. Example: ['*', '!letter-spacing']
    • Combine the "not" prefix with the other prefixes. Example: ['', '!font']
  • viewportUnit (String) Expected units.
  • fontViewportUnit (String) Expected units for font.
  • selectorBlackList (Array) The selectors to ignore and leave as px.
    • If value is string, it checks to see if selector contains the string.
      • ['body'] will match .body-class
    • If value is regexp, it checks to see if the selector matches the regexp.
      • [/^body$/] will match body but not .body
  • minPixelValue (Number) Set the minimum pixel value to replace.
  • mediaQuery (Boolean) Allow px to be converted in media queries.
  • replace (Boolean) replaces rules containing vw instead of adding fallbacks.
  • exclude (Regexp or Array of Regexp) Ignore some files like 'node_modules'
    • If value is regexp, will ignore the matches files.
    • If value is array, the elements of the array are regexp.
  • include (Regexp or Array of Regexp) If include is set, only matching files will be converted, for example, only files under src/mobile/ (include: /\/src\/mobile\//)
    • If the value is regexp, the matching file will be included, otherwise it will be excluded.
    • If value is array, the elements of the array are regexp.
  • landscape (Boolean) Adds @media (orientation: landscape) with values converted via landscapeWidth.
  • landscapeUnit (String) Expected unit for landscape option
  • landscapeWidth (Number) Viewport width for landscape orientation.

exclude and include can be set together, and the intersection of the two rules will be taken.


You can use special comments for ignore conversion of single lines:

  • /* px-to-viewport-ignore-next */ — on a separate line, prevents conversion on the next line.
  • /* px-to-viewport-ignore */ — after the property on the right, prevents conversion on the same line.


/* example input: */
.class {
  /* px-to-viewport-ignore-next */
  width: 10px;
  padding: 10px;
  height: 10px; /* px-to-viewport-ignore */
  border: solid 2px #000; /* px-to-viewport-ignore */

/* example output: */
.class {
  width: 10px;
  padding: 3.125vw;
  height: 10px;
  border: solid 2px #000;

There are several more reasons why your pixels may not convert, the following options may affect this: propList, selectorBlackList, minPixelValue, mediaQuery, exclude, include.

Use with PostCss configuration file

add to your postcss.config.js

module.exports = {
  plugins: {
    // ...
    'postcss-px-to-viewport': {
      // options

Use with gulp-postcss

add to your gulpfile.js:

var gulp = require('gulp');
var postcss = require('gulp-postcss');
var pxtoviewport = require('postcss-px-to-viewport');

gulp.task('css', function () {

    var processors = [
            viewportWidth: 320,
            viewportUnit: 'vmin'

    return gulp.src(['build/css/**/*.css'])


Please read [Code of Conduct](CODE-OF-CONDUCT.md) and [Contributing Guidelines](CONTRIBUTING.md) for submitting pull requests to us.

Running the tests

In order to run tests, you need to install dev-packages:

$ npm install

Then run the tests via npm script:

$ npm run test


The changelog is [here](CHANGELOG.md).


We use SemVer for versioning. For the versions available, see the tags on this repository.


See also the list of contributors who participated in this project.


This project is licensed under the [MIT License](LICENSE).


Visit Evrone website to get more information about the projects build.


*Note that all licence references and agreements mentioned in the postcss-px-to-viewport README section above are relevant to that project's source code only.