Math.acosh()

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.acosh() static method returns the inverse hyperbolic cosine of a number. That is,

∀x≥1,𝙼𝚊𝚝𝚑.𝚊𝚌𝚘𝚜𝚑(𝚡)=arcosh(x)=the unique y≥0 such that cosh(y)=x=ln(x+x2−1)\begin{aligned}\forall x \geq 1,\;\mathtt{\operatorname{Math.acosh}(x)} &= \operatorname{arcosh}(x) = \text{the unique } y \geq 0 \text{ such that } \cosh(y) = x\\&= \ln\left(x + \sqrt{x^2 - 1}\right)\end{aligned}

Try it

console.log(Math.acosh(0.999999999999));
// Expected output: NaN

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

console.log(Math.acosh(2));
// Expected output: 1.3169578969248166

console.log(Math.acosh(2.5));
// Expected output: 1.566799236972411

Syntax

Math.acosh(x)

Parameters

A number greater than or equal to 1.

Return value

The inverse hyperbolic cosine of x. If x is less than 1, returns NaN.

Description

Because acosh() is a static method of Math, you always use it as Math.acosh(), rather than as a method of a Math object you created (Math is no constructor).

Examples

Using Math.acosh()

js
Math.acosh(0); // NaN
Math.acosh(1); // 0
Math.acosh(2); // 1.3169578969248166
Math.acosh(Infinity); // Infinity

Specifications

Specification

ECMAScript® 2027 Language Specification
# sec-math.acosh

Browser compatibility

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This page was last modified on Jul 10, 2025 by MDN contributors.

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Standard built-in objects
Math
Static methods
Static properties
1. E
2. LN2
3. LN10
4. LOG2E
5. LOG10E
6. PI
7. SQRT1_2
8. SQRT2