Table of Contents
Getting started with JS math ceiling
ceil() method is a math function that rounds a number up to the nearest integer. This can be useful when you need to work with whole numbers in your code. In this article, we'll show you how to use the
Syntax of math.ceil()
Using the ceil property of the Math object, you can round up the value of the variable dist.
The ceil property has the following syntax:
This will round up any floating-point number to the nearest integer.
When should we use ceil() over round()?
There are functions like
Math.ceil (for “ceiling,” which rounds up to a whole number) and
Math.round (to the nearest whole number). We use
math.ceil to turn decimals into integers. There are different ways to turn decimals into integers. Sometimes you will want to round a number. This you can do with the round() method:
let x = 6.78; let y = 5.34; console.log("X:", x, "becomes", Math.round(x)); console.log("Y:", y, "becomes", Math.round(y));
This will log:
X: 6.78 becomes 7 Y: 5.34 becomes 5
As you can see it is using normal rounding here. It is also possible that you don't want to round down, but up. For example, if you need to calculate how many wood boards you need and you conclude that you need
1 is not going to be enough to do the job. You'll need
2. In this case, you can use the
ceil() method (referring to ceiling):
console.log("X:", x, "becomes", Math.ceil(x)); console.log("Y:", y, "becomes", Math.ceil(y));
This will log:
X: 6.78 becomes 7 Y: 5.34 becomes 6
How to use
ceil with negative numbers?
ceil() method is always rounding up to the first integer it encounters. We have used this before when we were generating random numbers! Careful with negative numbers here, because
-5 is higher than
-6. This is how it works, as you can see in this example:
let negativeX = -x; let negativeY = -y; console.log("negativeX:", negativeX, "becomes", Math.ceil(negativeX)); console.log("negativeY:", negativeY, "becomes", Math.ceil(negativeY));
This will log:
negativeX: -6.78 becomes -6 negativeY: -5.34 becomes -5
Round up using
Mathematics allows us to round up or down numbers, but to round down numbers, there are different approaches to doing that. However, if we want to round up numbers, the only appropriate method is the
ceil method. We can use the
round() method, but it is only when the decimal point of the number is greater than or equal to 0.5, it rounds up to the next higher absolute value.
If we want to round the number regardless of whether the number is greater than 0.5 or not, we can use the
ceil() method. So, if the value is
4.01, and we apply the
ceil method, it will return
5. In summary, the
ceil method rounds up and returns the next integer higher than the number (higher absolute value).
Let’s see this action with some code.
number1 = 4.01; number2 = 3.98; number3 = 123.45; console.log(Math.ceil(number1)); console.log(Math.ceil(number2)); console.log(Math.ceil(number3));
5 4 124
As you can see regardless of how far (decimally) the number is from the higher (or next) absolute value, it will round up to it via the
ceil() method via the
Math object. The typical rounding of numbers can either be up or down. However, if we want to round up, the
ceil method gives us the result we want.