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Number.prototype.toPrecision()

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

Try it

Syntax

toPrecision()
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 Language Specification # sec-number.prototype.toprecision

Browser compatibility

	Desktop						Mobile						Server
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	WebView Android	Chrome Android	Firefox for Android	Opera Android	Safari on IOS	Samsung Internet	Deno	Node.js
`toPrecision`	1	12	1	5.5	7	2	4.4	18	4	10.1	1	1.0	1.0	0.10.0