Math.atanh()

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.atanh() static method returns the inverse hyperbolic tangent of a number. That is,

∀x∊(−1,1),𝙼𝚊𝚝𝚑.𝚊𝚝𝚊𝚗𝚑(𝚡)=artanh(x)=the unique y such that tanh(y)=x=12ln(1+x1−x)\begin{aligned}\forall x \in ({-1}, 1),\;\mathtt{\operatorname{Math.atanh}(x)} &= \operatorname{artanh}(x) = \text{the unique } y \text{ such that } \tanh(y) = x \\&= \frac{1}{2}\,\ln\left(\frac{1+x}{1-x}\right)\end{aligned}

Example

console.log(Math.atanh(-1));
// Expected output: -Infinity

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

console.log(Math.atanh(0.5));
// Expected output: 0.549306144334055 (approximately)

console.log(Math.atanh(1));
// Expected output: Infinity

Syntax

js
Math.atanh(x)

Parameters

x

A number between -1 and 1, inclusive.

Return value

The inverse hyperbolic tangent of x. If x is 1, returns Infinity. If x is -1, returns -Infinity. If x is less than -1 or greater than 1, returns NaN.

Description

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

Examples

Using Math.atanh()

js
Math.atanh(-2); // NaN
Math.atanh(-1); // -Infinity
Math.atanh(-0); // -0
Math.atanh(0); // 0
Math.atanh(0.5); // 0.5493061443340548
Math.atanh(1); // Infinity
Math.atanh(2); // NaN

Specifications

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

Browser compatibility

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
atanh

See also