Math.floor() Method in JS – How to Round Down Numbers

Whenever you invoke Math.floor(), the method rounds down its argument to the nearest integer.

note

• Math.floor() is one of the built-in methods of the global Math object.
• The global Math object is one of the standard built-in JavaScript objects.

Syntax of the Math.floor() Method

Math.floor() accepts only one argument. Here is the syntax:

Math.floor(value);

The value argument represents the number you wish to floor (round down) to the nearest integer.

note

• Suppose the value argument is already an integer. In that case, Math.floor() will return the same number.
• Math.floor() is equivalent to -Math.ceil(-value).

Examples

Below are examples of the Math.floor() method.

How to round down 9 to the nearest integer

Math.floor(9);

// The invocation above will return: 9

Try it on StackBlitz

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How to round down 9.999 to the nearest integer

Math.floor(9.999);

// The invocation above will return: 9

Try it on StackBlitz

How to round down -9.999 to the nearest integer

Math.floor(-9.999);

// The invocation above will return: -10

Try it on StackBlitz

The snippet above returned -10 because -10 is the integer directly below -9.999 on the number line. In other words, -9 is greater than -9.999. But -10 is less than -9.999.

How to round down 0.91 to the nearest integer

Math.floor(0.91);

// The invocation above will return: 0

Try it on StackBlitz

tip

• To round up a number, use Math.ceil().
• To generate random numbers, use Math.random().

Overview

This article discussed what JavaScript's Math.floor() method does. We also used examples to see how it works.

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