UnitFormat.js

UnitFormat.js is a number formatter for human readable unit numbers, like 10km, 5GB, 17kHz, 220MW, ... with known metric suffixes.

Usage

The interface of UnitFormat.js is a single function that basically takes the number to be formatted and optionally the base unit, like "m" for meters:

let a = unitFormat(1000, "m") // 1km
let b = unitFormat(20000, "Hz") // 20kHz
let c = unitFormat(1000) // 1k
let d = unitFormat(0.02, "m") // 2cm 

Installation

Installing UnitFormat.js is as easy as cloning this repo or use the following command:

npm install unitformat

Available Parameters

The whole package consists of a single function UnitFormat with the following signature

UnitFormat(num, baseUnit="", prefixes="kMGTPE", base=10)

• num: the number to be formatted
• baseUnit: the base unit, like meters, Hertz, Joule, ...
• suffix: which suffixes should be used
• base: The number base, default is 10, but 2 is also possible for bytes

Suffixes

The suffix parameter is a string list of single-character metric prefixes, like kMGTPE. For base 10 the following prefixes can be used:

• E: Exa
• P: Peta
• T: Tera
• G: Giga
• M: Mega
• k: Kilo
• h: Hecto
• d: Deci
• c: Centi
• m: Milli
• u: Micro
• n: Nano
• p: Pico
• f: Femto
• a: Atto

And for base 2 the following prefixes are possible:

• k: Kilo
• M: Mega
• G: Giga
• T: Tera
• P: Peta
• E: Exa

Using UnitFormat.js with the browser

<script src="unitformat.min.js"></script>
<script>
  var x = UnitFormat(10000);
</script>

Coding Style

As every library I publish, UnitFormat.js is also built to be as small as possible after compressing it with Google Closure Compiler in advanced mode. Thus the coding style orientates a little on maxing-out the compression rate. Please make sure you keep this style if you plan to extend the library.

Building the library

After cloning the Git repository run:

npm install
npm run build

Run a test

Testing the source against the shipped test suite is as easy as

npm run test

Copyright and licensing

Copyright (c) 2025, Robert Eisele Licensed under the MIT license.