Web/JavaScript/Reference/Global objects/Number/toPrecision

The toPrecision() method returns a string representing the Number object to the specified precision.

Syntax

numObj.toPrecision([precision])

Parameters

precision Optional

An integer specifying the number of significant digits.

Return value

A string representing a Number object in fixed-point or exponential notation rounded to precision significant digits. See the discussion of rounding in the description of the Number.prototype.toFixed() method, which also applies to toPrecision().

If the precision argument is omitted, behaves as Number.prototype.toString(). If the precision argument is a non-integer value, it is rounded to the nearest integer.

Exceptions

RangeError

If precision is not between 1 and 100 (inclusive), a RangeError is thrown. Implementations are allowed to support larger and smaller values as well. ECMA-262 only requires a precision of up to 21 significant digits.

Examples

Using toPrecision

let numObj = 5.123456

console.log(numObj.toPrecision())    // logs '5.123456'
console.log(numObj.toPrecision(5))   // logs '5.1235'
console.log(numObj.toPrecision(2))   // logs '5.1'
console.log(numObj.toPrecision(1))   // logs '5'

numObj = 0.000123

console.log(numObj.toPrecision())    // logs '0.000123'
console.log(numObj.toPrecision(5))   // logs '0.00012300'
console.log(numObj.toPrecision(2))   // logs '0.00012'
console.log(numObj.toPrecision(1))   // logs '0.0001' 

// note that exponential notation might be returned in some circumstances
console.log((1234.5).toPrecision(2)) // logs '1.2e+3'

Specifications

Specification

ECMAScript (ECMA-262)The definition of 'Number.prototype.toPrecision' in that specification.

Browser compatibility

The compatibility table in this page is generated from structured data. If you'd like to contribute to the data, please check out https://github.com/mdn/browser-compat-data and send us a pull request.

Update compatibility data on GitHub

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet	Node.js
toPrecision	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 5.5	Opera Full support 7	Safari Full support 2	WebView Android Full support 1	Chrome Android Full support 18	Firefox Android Full support 4	Opera Android Full support 10.1	Safari iOS Full support 1	Samsung Internet Android Full support 1.0	nodejs Full support 0.1.100

Legend

Full support  

Full support

See also

• Number.prototype.toFixed()
• Number.prototype.toExponential()
• Number.prototype.toString()

Number.prototype.toPrecision() by Mozilla Contributors is licensed under CC-BY-SA 2.5.