Number.prototype.toPrecision()

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 toPrecision() method of Number values returns a string representing this number to the specified number of significant digits.

Try it

Syntax

toPrecision()
toPrecision(precision)

Parameters

precision Optional: An integer specifying the number of significant digits.
TypeError: Thrown if this method is invoked on an object that is not a Number.

Return value

A string representing the given number, using the given number of significant digits. Scientific notation is used if the exponent is greater than or equal to precision or less than -6. Has the same behavior as Number.prototype.toString() if the precision argument is omitted.

Exceptions

RangeError: Thrown if precision is not between 1 and 100 (inclusive).

Examples

Using `toPrecision`

// This number has exponent 0, so it will never use exponential notation
let num = 5.123456;

console.log(num.toPrecision()); // '5.123456'
console.log(num.toPrecision(5)); // '5.1235'
console.log(num.toPrecision(2)); // '5.1'
console.log(num.toPrecision(1)); // '5'

// This number has exponent -4, so it will never use exponential notation
num = 0.000123;

console.log(num.toPrecision()); // '0.000123'
console.log(num.toPrecision(5)); // '0.00012300'
console.log(num.toPrecision(2)); // '0.00012'
console.log(num.toPrecision(1)); // '0.0001'

// This number has exponent 3, so it will use exponential notation if precision is less than 4
num = 1234.5;
console.log(num.toPrecision(1)); // '1e+3'
console.log(num.toPrecision(2)); // '1.2e+3'
console.log(num.toPrecision(6)); // '1234.50'

// This number has exponent -7, so it will always use exponential notation
num = 0.00000012345;
console.log(num.toPrecision(1)); // '1e-7'
console.log(num.toPrecision(10)); // '1.234500000e-7'

Specifications

Specification
ECMAScript Language Specification # sec-number.prototype.toprecision

Browser compatibility

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