# Is postcss-calc ESM-only? Can you require() it?

> postcss-calc@11.1.1 is ESM-only. ESM-only since 11.0.0 — last CommonJS version is 10.1.1.

PostCSS plugin to reduce calc()

Last verified Sep 9, 2026 against postcss-calc@11.1.1.

postcss-calc dropped its CommonJS build in 11.0.0 (August 2026). The last version with a plain require()-able CommonJS entry is 10.1.1, published Jan 31, 2025; it declares support for Node.js ^18.12 || ^20.9 || >=22.0.

On Node.js 22.12+ and newer (postcss-calc@11.1.1 declares Node.js ^22.22.3 || ^24.15 || >=26.0), require("postcss-calc") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26. Node.js 18 has no require(esm), and postcss-calc@11.1.1 declares Node.js ^22.22.3 || ^24.15 || >=26.0, so 18 is outside its supported range anyway.

postcss-calc@11.1.1 declares engines "^22.22.3 || ^24.15 || >=26.0", so Node.js 18, 20 are outside its supported range regardless of module format.

## What to do

1. On Node.js 22.12+ and newer (postcss-calc@11.1.1 declares Node.js ^22.22.3 || ^24.15 || >=26.0), require("postcss-calc") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26.
2. From a CommonJS file, use a dynamic import inside an async function: const postcssCalc = await import("postcss-calc"). That works on every Node.js version the package supports (^22.22.3 || ^24.15 || >=26.0).
3. If you need a synchronous require() or run Node.js 18: npm install postcss-calc@10.1.1, the last CommonJS release (published Jan 31, 2025); it declares Node.js ^18.12 || ^20.9 || >=22.0.
4. postcss-calc@11.1.1 declares engines "^22.22.3 || ^24.15 || >=26.0", so Node.js 18, 20 are unsupported regardless: upgrade Node.js or pin an older release.
5. TypeScript: types are bundled; install nothing extra.

## Facts

- Latest: 11.1.1 (Sep 7, 2026)
- Module format: ESM-only
- Last CommonJS version: 10.1.1
- ESM-only since: 11.0.0 (Aug 20, 2026)
- TypeScript types: bundled
- Node engines: ^22.22.3 || ^24.15 || >=26.0
- Weekly downloads: 12.4M
- License: MIT

## Runtime test results for postcss-calc@11.1.1

Installed and executed on Sep 9, 2026 with require("postcss-calc") from a CommonJS file and import "postcss-calc" from an ES module.

| Runtime | require("postcss-calc") | import "postcss-calc" |
|---|---|---|
| Node.js 18 | fails (ERR_REQUIRE_ESM) | works |
| Node.js 20 | works | works |
| Node.js 22 | works | works |
| Node.js 24 | works | works |
| Node.js 26 | works | works |
| Bun 1.4.0 | works | works |

## How to import postcss-calc

ES modules:

```js
import * as postcssCalc from "postcss-calc";
```

Namespace import shown because the ESM entry may have no default export; use named imports for what it exports.

CommonJS:

```js
// Node.js 22.12+ and newer (verified):
const postcssCalc = require("postcss-calc");

// Any Node.js version the package supports (^22.22.3 || ^24.15 || >=26.0), from an async function:
async function main() {
  const postcssCalc = await import("postcss-calc");
}

// Or pin the last CommonJS release (declares Node.js ^18.12 || ^20.9 || >=22.0):
// npm install postcss-calc@10.1.1
```

## Module format by version

Derived from the type, main and exports fields of every stable release on npm (43 versions; the newest 43 shown).

| Versions | Format | First published |
|---|---|---|
| 11.0.0 – 11.1.1 | ESM-only | Aug 20, 2026 |
| 1.0.0 – 10.1.1 | CommonJS | Aug 4, 2014 |

## Frequently asked

**Is postcss-calc ESM-only?**

postcss-calc@11.1.1 is ESM-only. postcss-calc dropped its CommonJS build in 11.0.0 (August 2026). The last version with a plain require()-able CommonJS entry is 10.1.1, published Jan 31, 2025; it declares support for Node.js ^18.12 || ^20.9 || >=22.0.

**Which version of postcss-calc still supports CommonJS / require()?**

10.1.1 is the last version of postcss-calc with a CommonJS build; it declares Node.js ^18.12 || ^20.9 || >=22.0. Install it with "npm install postcss-calc@10.1.1". Every version from 11.0.0 on is ESM-only.

**How do I use postcss-calc from a CommonJS file?**

From a CommonJS file, use a dynamic import inside an async function: const postcssCalc = await import("postcss-calc"). That works on every Node.js version the package supports (^22.22.3 || ^24.15 || >=26.0). On Node.js 22.12+ and newer (postcss-calc@11.1.1 declares Node.js ^22.22.3 || ^24.15 || >=26.0), require("postcss-calc") works with the latest version: Node.js loads synchronous ES modules through require(). Verified on Node.js 22, 24 and 26. Alternatively pin postcss-calc@10.1.1 (declares Node.js ^18.12 || ^20.9 || >=22.0).

**Does postcss-calc work in Bun?**

Yes. import "postcss-calc" loaded successfully in Bun 1.4.0 on Sep 9, 2026.

**Does postcss-calc ship TypeScript types?**

Yes. postcss-calc bundles its own type declarations; no @types package is needed.

## Links

- [postcss-calc on npm](https://www.npmjs.com/package/postcss-calc)
- [Source repository](https://github.com/postcss/postcss-calc)
- [HTML version](https://canirequire.com/package/postcss-calc/)
- [JSON version](https://canirequire.com/package/postcss-calc.json)

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