# What are the differences between JavaScript's Math.floor() and Math.ceil()?Ava W

JavaScript's`Math.floor()`

and`Math.ceil()`

are both methods of the`Math`

object used for rounding numbers. Here are the differences between these two methods:
1.`Math.floor()`

:
- The`Math.floor()`

method rounds a number down to the nearest integer less than or equal to the given value.
- It always returns the largest integer less than or equal to the input value.

`1 2 3 4`

`Math.floor(4.9); // 4 Math.floor(-2.1); // -3`

In the first example,`Math.floor(4.9)`

returns`4`

because`4`

is the largest integer less than or equal to`4.9`

. In the second example,`Math.floor(-2.1)`

returns`-3`

because`-3`

is the largest integer less than or equal to`-2.1`

.
2.`Math.ceil()`

:
- The`Math.ceil()`

method rounds a number up to the nearest integer greater than or equal to the given value.
- It always returns the smallest integer greater than or equal to the input value.

`1 2 3 4`

`Math.ceil(4.9); // 5 Math.ceil(-2.1); // -2`

In the first example,`Math.ceil(4.9)`

returns`5`

because`5`

is the smallest integer greater than or equal to`4.9`

. In the second example,`Math.ceil(-2.1)`

returns`-2`

because`-2`

is the smallest integer greater than or equal to`-2.1`

.
**3. Usage scenarios:**
-`Math.floor()`

is commonly used when you need to round down a number to the nearest integer. It is useful in situations like calculating array indices or truncating decimal places.
-`Math.ceil()`

is often used when you want to round up a number to the nearest integer. It is useful, for example, in calculations where you need to ensure that a value is not rounded down.
**4. Comparison:**
- When dealing with positive numbers,`Math.floor()`

always rounds towards zero (downward), while`Math.ceil()`

always rounds away from zero (upward).
- For negative numbers, the behavior is inverted.`Math.floor()`

rounds further away from zero (more negative), and`Math.ceil()`

rounds closer to zero (less negative).

`1 2 3 4`

`Math.floor(-3.5); // -4 Math.ceil(-3.5); // -3`

In this example,`Math.floor(-3.5)`

returns`-4`

because it rounds further away from zero, while`Math.ceil(-3.5)`

returns`-3`

because it rounds closer to zero.
Choose the appropriate method based on your rounding needs. If you want to round down to the nearest integer, use`Math.floor()`

. If you need to round up to the nearest integer, use`Math.ceil()`

.

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