# Let's talk about Math.ceil, Math.floor, and Math.round 🌿

## Introduction

We all have learned about rounding off numbers in our school. We usually increase the integer if its value is >=.5 and decrease it, if it is <= .4.

> 1.5 ≈ 2
>
> 1.4 ≈ 1

We all know JavaScript has a built-in object called Math, which has properties and methods for mathematical constants and functions. 

We have three methods that are mostly used to round off a number in JS, i.e., `Math.ceil()`, `Math.floor()`, `Math.round()`. Let's explore them in this article.

![](https://media.giphy.com/media/U5D3QY0QQWsR0nhwmg/giphy.gif)

## 🎳 Math.ceil 

`Math.ceil` function in JavaScript is used to round of a number that is passed into it to its nearest integer in upward direction of rounding. What to I mean by upward direction? Towards the greater value. `Math.ceil()` takes only one parameter that is the value to be rounded.  So, if we have a value of 1.4, `Math.ceil()` will round off it to 2.

```javascript
console.log(Math.ceil(1.4)); 
//2
console.log(Math.ceil(1.6)); 
// 2
console.log(Math.round(-1.4));
// 1
console.log(Math.round(-1.6));
// 1
```

![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/fa/Ceiling_function.svg/800px-Ceiling_function.svg.png)*Photo from [Wikipedia](https://en.wikipedia.org/wiki/Floor_and_ceiling_functions#/media/File:Ceiling_function.svg)*

## 🎳 Math.floor()

Where the `Math.ceil` method returns the smallest integer greater than or equal to the value we pass, `Math.floor` returns the largest or equal integer less than the given value. It also takes a single parameter. 

![](https://upload.wikimedia.org/wikipedia/commons/thumb/e/e1/Floor_function.svg/800px-Floor_function.svg.png)*Photo from [Wikipedia](https://en.wikipedia.org/wiki/Floor_and_ceiling_functions#/media/File:Floor_function.svg)*

So, if we pass the same value 1.4 in `Math.floor`, we'll get 1 in return. Even if we pass 1.6, we'll also get 1.

```javascript
console.log(Math.floor(1.4));
// 1
console.log(Math.floor(1.6));
// 1
console.log(Math.floor(-1.4));
// -2
console.log(Math.floor(-1.6));
// -2
```

## 🎳 Math.round()

`Math.round()` rounds off the number depending on the fractional part of the number. So, if the fractional part is >=.5, it'll return the smallest integer greater than the passed value and if the number is <=.4 we'll get the largest integer smaller than the number we pass. 

```javascript
console.log(Math.round(1.4));
// 1
console.log(Math.round(1.6));
// 2
console.log(Math.round(1.5)); 
// 2
console.log(Math.round(-1.4));
// -1
console.log(Math.round(-1.6));
// -2
console.log(Math.round(-1.5));
// 2
```

So, Math.round() can go both upward and downward depending on the fractional Part.

![](https://i.ibb.co/YcZbNhd/mathfloor.png)

## 🎳 Math.trunc()

There's another method available in JS Math object that is `Math.trunc()`. `Math.trunc()` returns the integer part of a number by removing any fractional part of the number.

```javascript
console.log(Math.trunc(1.4));
// 1
console.log(Math.trunc(1.6));
// 1
console.log(Math.trunc(-1.4));
// 1
console.log(Math.trunc(-1.6));
// 1
```

## Conclusion

Rounding off numbers is an essential part of programming. I hope this article revisited your memories about different built-in rounding off methods we have in JavaScript. Leave an ❤ if you found this article helpful. 😊