Math.log2()

Baseline Widely available

This feature is well established and works across many devices and browser versions. It’s been available across browsers since July 2015.

The Math.log2() static method returns the base 2 logarithm of a number. That is

x>0,𝙼𝚊𝚝𝚑.𝚕𝚘𝚐𝟸(𝚡)=log2(x)=the unique y such that 2y=x\forall x > 0,\;\mathtt{\operatorname{Math.log2}(x)} = \log_2(x) = \text{the unique } y \text{ such that } 2^y = x

Try it

console.log(Math.log2(3));
// Expected output: 1.584962500721156

console.log(Math.log2(2));
// Expected output: 1

console.log(Math.log2(1));
// Expected output: 0

console.log(Math.log2(0));
// Expected output: -Infinity

Syntax

js
Math.log2(x)

Parameters

x

A number greater than or equal to 0.

Return value

The base 2 logarithm of x. If x < 0, returns NaN.

Description

Because log2() is a static method of Math, you always use it as Math.log2(), rather than as a method of a Math object you created (Math is not a constructor).

This function is the equivalent of Math.log(x) / Math.log(2). For log2(e), use the constant Math.LOG2E, which is 1 / Math.LN2.

Examples

Using Math.log2()

js
Math.log2(-2); // NaN
Math.log2(-0); // -Infinity
Math.log2(0); // -Infinity
Math.log2(1); // 0
Math.log2(2); // 1
Math.log2(3); // 1.584962500721156
Math.log2(1024); // 10
Math.log2(Infinity); // Infinity

Specifications

Specification
ECMAScript® 2025 Language Specification
# sec-math.log2

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
Chrome
Edge
Firefox
Opera
Safari
Chrome Android
Firefox for Android
Opera Android
Safari on iOS
Samsung Internet
WebView Android
WebView on iOS
Deno
Node.js
log2

Legend

Tip: you can click/tap on a cell for more information.

Full support
Full support

See also