Math.fround()

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.fround() static method returns the nearest 32-bit single precision float representation of a number.

Try it

console.log(Math.fround(5.5));
// Expected output: 5.5

console.log(Math.fround(5.05));
// Expected output: 5.050000190734863

console.log(Math.fround(5));
// Expected output: 5

console.log(Math.fround(-5.05));
// Expected output: -5.050000190734863

Syntax

js
Math.fround(doubleFloat)

Parameters

doubleFloat

A number.

Return value

The nearest 32-bit single precision float representation of doubleFloat.

Description

JavaScript uses 64-bit double floating-point numbers internally, which offer a very high precision. However, sometimes you may be working with 32-bit floating-point numbers, for example if you are reading values from a Float32Array. This can create confusion: checking a 64-bit float and a 32-bit float for equality may fail even though the numbers are seemingly identical.

To solve this, Math.fround() can be used to cast the 64-bit float to a 32-bit float. Internally, JavaScript continues to treat the number as a 64-bit float, it just performs a "round to even" on the 23rd bit of the mantissa, and sets all following mantissa bits to 0. If the number is outside the range of a 32-bit float, Infinity or -Infinity is returned.

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

Examples

Using Math.fround()

The number 1.5 can be precisely represented in the binary numeral system, and is identical in 32-bit and 64-bit:

js
Math.fround(1.5); // 1.5
Math.fround(1.5) === 1.5; // true

However, the number 1.337 cannot be precisely represented in the binary numeral system, so it differs in 32-bit and 64-bit:

js
Math.fround(1.337); // 1.3370000123977661
Math.fround(1.337) === 1.337; // false

21502^150 is too big for a 32-bit float, so Infinity is returned:

js
2 ** 150; // 1.42724769270596e+45
Math.fround(2 ** 150); // Infinity

Specifications

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

Browser compatibility

Report problems with this compatibility data on GitHub
desktopmobileserver
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
fround

Legend

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Full support
Full support

See also