Web/JavaScript/Reference/Global objects/parseFloat

The parseFloat() function parses an argument (converting it to a string first if needed) and returns a floating point number.

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Syntax

parseFloat(string)

Parameters

string

The value to parse. If this argument is not a string, then it is converted to one using the ToString abstract operation. Leading whitespace in this argument is ignored.

Return value

A floating point number parsed from the given string.

Or NaN when the first non-whitespace character cannot be converted to a number.

Description

parseFloat is a function property of the global object.

• If parseFloat encounters a character other than a plus sign (+), minus sign (- U+002D HYPHEN-MINUS), numeral (0–9), decimal point (.), or exponent (e or E), it returns the value up to that character, ignoring the invalid character and characters following it.
• A second decimal point also stops parsing (characters up to that point will still be parsed).
• Leading and trailing spaces in the argument are ignored.
• If the argument’s first character can’t be converted to a number (it’s not any of the above characters), parseFloat returns NaN.
• parseFloat can also parse and return Infinity.
• parseFloat converts BigInt syntax to Numbers, losing precision. This happens because the trailing n character is discarded.

Consider Number(value) for stricter parsing, which converts to NaN for arguments with invalid characters anywhere.

parseFloat will parse non-string objects if they have a toString or valueOf method. The returned value is the same as if parseFloat had been called on the result of those methods.

Examples

parseFloat returning a number

The following examples all return 3.14:

parseFloat(3.14);
parseFloat('3.14');
parseFloat('  3.14  ');
parseFloat('314e-2');
parseFloat('0.0314E+2');
parseFloat('3.14some non-digit characters');
parseFloat({ toString: function() { return "3.14" } });

parseFloat returning NaN

The following example returns NaN:

parseFloat('FF2');

parseFloat and BigInt

The following examples both return 900719925474099300, losing precision as the integer is too large to be represented as a float:

parseFloat(900719925474099267n);
parseFloat('900719925474099267n');

Specifications

Specification
ECMAScript (ECMA-262)The definition of 'parseFloat' in that specification.

Browser compatibility

The compatibility table on 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
parseFloat	Chrome Full support 1	Edge Full support 12	Firefox Full support 1	IE Full support 3	Opera Full support 3	Safari Full support 1	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

• parseInt()
• Number.parseFloat()
• Number.parseInt()
• Number.toFixed()
• isNaN()

parseFloat() by Mozilla Contributors is licensed under CC-BY-SA 2.5.