Python round to nearest integer

Python: Round a Number to the Nearest Integer

In many situations, you will find yourself in a situation where you want to round a floating-point number to the nearest integer in your Python 3 code. In this article, I will explain how.

1. Using the Round() Function

You can use the Round built-in function in Python to round a number to the nearest integer.

>>> round(2.4) 2 >>> round(2.6) 3 >>> round(2.5) 2

Note that in Python 3, the return type is int. However, if you are still on Python 2, the return type will be a float so you would need to cast the returned value into int.

Another thing to notice here is that according to Python’s documentation, any floating number that is mid-way between two integers (e.g. 2.5, 3.4. etc…) will be rounded to the nearest even choice. For example:

2. Without Using any Built-in Functions

If you want to round a number to the nearest integer without using any built-in functions in Python (maybe for a coding interview or something), then you can define the following function.

def round_number(x): if (x - int(x)) < 0.5: return int(x) else: return int(x) + 1

There you go! Happy Python coding 🙂

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Python Round to Int – How to Round Up or Round Down to the Nearest Whole Number

Ihechikara Vincent Abba

When working with float values (numbers with decimal values) in our Python program, we might want to round them up or down, or to the nearest whole number.

In this article, we'll see some built-in functionalities that let us round numbers in Python. And we'll see how to use them with some examples.

We'll start with the round() function. By default, it rounds a number to the nearest whole number. We'll also see how to use the function's parameters to change the type of result returned to us.

We'll then talk about the math.ceil() and math.floor() methods which rounds up and rounds down a number to the nearest whole number/integer respectively. These two methods are from the built-in math module in Python.

How to Use the round() Function to Round to the Nearest Whole Number

The round() function takes in two parameters. Here's what the syntax looks like:

round(number, decimal_digits)

The first parameter – number – is the number we are rounding to the nearest whole number.

The second parameter – decimal_digits – is the number of decimals to be returned. The default value is 0.

In our first example, we're using only one parameter – the number to be rounded, which is 2.56789 .

When we passed in the number variable to the round() function, it got rounded to the nearest whole number which is 3.

That's how easy it is to use!

Now, let's work with the second parameter.

x = 2.56789 print(round(x, 2)) # 2.57

The code above is similar to the last example except for the second parameter. We passed in a value of two. This will round the number to the nearest hundredth (two decimal places).

In our case, 2.57 was returned. That is, 2.56789 to 2.57.

Let's see one last example to fully understand how the second parameter works.

x = 2.56789 print(round(x, 3)) # 2.568 

Now, we've made the second parameter 3. We'll get the number rounded to the nearest thousandth (three decimal places).

The initial number – 2.56789 – was rounded to 2.568.

How to Use the math.ceil() Method to Round Up a Number to the Nearest Whole Number

The math.ceil() method simple takes in the number to be rounded up as its parameter. Here's what the syntax looks like:

import math x = 5.57468465 print(math.ceil(x)) # 6 

In the code above, you'll notice that we first imported the math module: import math . This give us access to all the methods provided by the module.

We created an x variable which has 5.57468465 as its value.

In order to round this number up to the nearest whole number, we passed in the number (in the x variable) to the math.ceil() method: math.ceil(x) .

The resulting value from this operation, as can be seen in the code above, is 6.

How to Use the math.floor() Method to Round Down a Number to the Nearest Whole Number

Just like we did in the last section, in order to use the math.floor() method, we must first import the math module.

Here's the syntax for math.floor() method:

import math x = 5.57468465 print(math.floor(x)) # 5

As expected, we passed in the number to be rounded down to the math.floor() method: math.floor(x) . The x variable has the number 5.57468465 stored in it.

This number got rounded down to 5.

Conclusion

In this article, we talked about three built-in functionalities in Python that let us round numbers.

The round() function rounds a number to the nearest whole number.

The math.ceil() method rounds a number up to the nearest whole number while the math.floor() method rounds a number down to the nearest whole number. These two methods are both accessible through the math module.

With the examples given in each section, we were able to see how to use each functionality to obtain our desired result.

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Python round() Function

The round() function returns a floating point number that is a rounded version of the specified number, with the specified number of decimals.

The default number of decimals is 0, meaning that the function will return the nearest integer.

Syntax

Parameter Values

Parameter	Description
number	Required. The number to be rounded
digits	Optional. The number of decimals to use when rounding the number. Default is 0

More Examples

Example

Round to the nearest integer:

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