JavaScript (ES2026) reference · Math Methods and Constants

JavaScript Math.log2() Method

Return the base-2 logarithm of a number, e.g. how many bits or how many halvings are needed.

JavaScript (ES2026) Since ES2015

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Syntax

Math.log2(x)

Parameter	Description
`x`	A number.

A number.

Powers of twoTry it yourself

console.log(Math.log2(8), Math.log2(1024));

Output

3 10

Binary search stepsTry it yourself

const items = 1_000_000;
console.log("binary search steps:", Math.ceil(Math.log2(items)));

Output

binary search steps: 20

Version	Change
JavaScript ES2015	Added

Math.log() · Return the natural logarithm (base e) of a number; divide by Math.log(base) to get a logarithm in any base.
Math.log10() · Return the base-10 logarithm of a number, e.g. to count digits or work with decibels.
JavaScript Math · tutorial
JavaScript Numbers · tutorial