Math.f16round()

Baseline 2025

Newly available

Since April 2025, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The Math.f16round() static method returns the nearest 16-bit half precision float representation of a number.

Try it

console.log(Math.f16round(5.5));
// Expected output: 5.5

console.log(Math.f16round(5.05));
// Expected output: 5.05078125

console.log(Math.f16round(5));
// Expected output: 5

console.log(Math.f16round(-5.05));
// Expected output: -5.05078125

Syntax

Math.f16round(doubleFloat)

Return value

The nearest 16-bit half precision float representation of doubleFloat.

Math.f16round is the 16-bit counterpart of Math.fround(). It is intended to smooth some rough edges when interacting with float16 numbers, such as when reading from a Float16Array. Internally, JavaScript continues to treat the number as a 64-bit float, it just performs a "round to even" on the 10th bit of the mantissa, and sets all following mantissa bits to 0. If the number is outside the range of a 16-bit float, Infinity or -Infinity is returned.

Because f16round() is a static method of Math, you always use it as Math.f16round(), rather than as a method of a Math object you created (Math is not a constructor).

Examples

Using Math.f16round()

The number 1.5 can be precisely represented in the binary numeral system, and is identical in 16-bit and 64-bit:

js
Math.f16round(1.5); // 1.5
Math.f16round(1.5) === 1.5; // true

However, the number 1.337 cannot be precisely represented in the binary numeral system, so it differs in 16-bit and 64-bit:

js
Math.f16round(1.337); // 1.3369140625
Math.f16round(1.337) === 1.337; // false

100000 is too big for a 16-bit float, so Infinity is returned:

Math.f16round(100000); // Infinity

Specifications

Specification

ECMAScript® 2027 Language Specification
# sec-math.f16round

Browser compatibility

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This page was last modified on Jul 10, 2025 by MDN contributors.

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Standard built-in objects
Math
Static methods
Static properties
1. E
2. LN2
3. LN10
4. LOG2E
5. LOG10E
6. PI
7. SQRT1_2
8. SQRT2

Math.f16round()

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