**Problem Formulation**: Given a float number. How to round the float up in Python?

Here are some examples of what you want to accomplish:

`42.42 --> 43`

`21.00001 --> 22`

`-0.1 --> 0`

Solution: If you have little time, here’s the most straightforward answer:

To round a number up in Python, import the `math`

library with `import math`

, and call `math.ceil(number)`

that returns the ceiling of `number`

, i.e., the smallest integer greater than or equal to `number`

.

In general, there are at least four ways to round a float number `x`

up in Python:

**Round up**: The`math.ceil(x)`

function rounds number`x`

up to the next full integer.**Round up (float representation)**: Alternatively,`numpy.ceil(x)`

rounds up and returns a float representation of the next full integer (e.g.,`2.0`

instead of`2`

).**Round down**: The`math.floor(x)`

function rounds number`x`

down to the next full integer.**Round up and down**: The Python built-in`round(x)`

function rounds`x`

up and down to the closest full integer.**Vanilla Python**: The one-liner expression

rounds`int(x) + ((int(x)!=x) if x>0 else 0)`

`x`

up*without external dependency*. An alternative is the expression`int(x) + bool(x%1)`

to round up positive numbers.

Let’s dive into each of those and more options in the remaining article. I guarantee you’ll get out of it having learned at least a few new Python tricks in the process!

Table of Contents

## Method 1: math.ceil()

To round a number up in Python, import the `math`

library with `import math`

, and call `math.ceil(number)`

.

The function returns the ceiling of the specified `number`

that is defined as the smallest integer greater than or equal to `number`

The following code shows how to round the number 42.42 up to 43, 21.00001 to 22, and -0.1 to 0 using the `math.ceil()`

function.

import math print(math.ceil(42.42)) # 43 print(math.ceil(21.00001)) # 22 print(math.ceil(-0.1)) # 0

The following video shows the `math.ceil()`

as well as the `math.floor()`

functions — feel free to watch it to gain a deeper understanding:

## Method 2: np.ceil()

To round a number up in Python, import the NumPy library with `import numpy as np`

, and call `np.ceil(number)`

.

The function returns the ceiling of the specified `number`

that is defined as the smallest integer greater than or equal to `number`

.

The following code shows how to round the number 42.42 up to 43, 21.00001 to 22, and -0.1 to 0 using the `np.ceil()`

function.

import numpy as np print(np.ceil(42.42)) # 43.0 print(np.ceil(21.00001)) # 22.0 print(np.ceil(-0.1)) # 0.0

Both `math.ceil()`

and `np.ceil()`

round up to the next full integer. The difference between `math.ceil()`

and `np.ceil()`

is that the former returns an integer and the latter returns a float value.

## Method 3: int(x) + bool(x%1)

You can also use the following vanilla Python snippet to round a number `x`

up to the next full integer:

- If
`x`

is negative, round up by calling`int(x)`

. - If
`x`

is positive, round up by calling`int(x) + bool(x%1)`

.

**Explanation**: Any non-zero expression passed into the `bool()`

function will yield `True`

which is represented by integer 1. The modulo expression `x%1`

returns the decimal part of `x`

. If it is non-zero, we add `bool(x%1) == 1`

, i.e., we round up. If it is zero, we add `bool(x%1) == 0`

, i.e., we’re already done.

Here’s what this looks like in a simple Python function:

def round_up(x): if x<0: return int(x) return int(x) + bool(x%1) print(round_up(42.42)) # 43 print(round_up(21.00001)) # 22 print(round_up(-0.1)) # 0

You can watch my explainer video on modulo here:

## Method 4: int(x) + int(x)!=x

If you don’t want to import the `math`

module, you can use the one-liner beauty:

`int(x) + ((int(x)!=x) if x>0 else 0)`

This ternary expression rounds up number `x`

to the next full integer. This first cuts off the decimal part using the `int()`

function and then adds one if there is a non-zero decimal part (and it’s a positive number) and zero otherwise.

If the number `x`

is negative, the expression `int(x)`

already rounds up to the next full integer.

def round_up(x): return int(x) + ((int(x)!=x) if x>0 else 0) print(round_up(42.42)) # 43 print(round_up(21.00001)) # 22 print(round_up(-0.1)) # 0

- The
`int()`

built-in function cuts of the decimal part, i.e., rounds down. - The expression
`int(x)!=x`

evaluates to 1 if the decimal part of`x`

is greater than 0. Otherwise, it becomes 0. - This helps us because only if the decimal part is greater than 0, we need to add +1 to the rounded-down number to round it up.
- If the number
`x`

is negative, the expression`int(x)`

already rounds up to the next full integer, so we use the ternary operator`(...) if (...) else (...)`

to account for this condition.

You can watch my introductory video on the **ternary operator** here:

## Method 5: round()

*This method is probably not exactly what you want because it rounds a number up and down, depending on whether the number is closer to the smaller or larger next full integer. However, I’ll still mention it for comprehensibility.*

Python’s built-in `round()`

function takes two input arguments:

- a
`number`

and - an optional
`precision`

in decimal digits.

It rounds the number to the given precision and returns the result. The return value has the same type as the input number—or integer if the `precision`

argument is omitted.

Per default, the precision is set to 0 digits, so `round(3.14)`

results in `3`

.

Here are three examples using the `round()`

function—that show that it doesn’t exactly solve our problem.

import math print(round(42.42)) # 42 print(round(21.00001)) # 21 print(round(-0.1)) # 0

Again, we have a video on the `round()`

function — feel free to watch for maximum learning!

## Method 6: Rounding Up After Integer Division

If the float to be rounded up comes from a division operation `a/b`

, you can also use integer division `a//b`

to round down to the next integer, and increment this by one. Thus, the expression `a//b+1`

rounds the resulting number up if `a`

is not divisible by `b`

, otherwise, the result of `a//b`

would already provide the “rounded-up” semantics.

You can create a simple ternary operator `x if y else z`

to differentiate between those two conditions:

a = int(input('a=')) b = int(input('b=')) rounded_up = a//b + 1 if a%b else a//b print(rounded_up)

The code goes through the following steps:

- Get the input strings from the user using the built-in
`input()`

function. - Convert the inputs to integer values using the built-in
`int()`

function. - Use the modulo operation
`a%b`

to differentiate between`b`

being a divisor of`a`

or not. - If not, the result will have a remainder and you can use integer division
`a//b`

to round down and increment this by one. - If yes, the result won’t have a remainder and you can simply use integer division because it, mathematically, would already be considered to be rounded up.
- You use the ternary operator to pack this logic into a single line of code.

Here’s an example execution that was rounded up:

a=8 b=3 3

And here’s an example execution that wasn’t:

a=8 b=4 2

An alternative one-liner to round up two integers would be the following beauty:

a = int(input('a=')) b = int(input('b=')) rounded_up = a // b + (a % b > 0) print(rounded_up)

The expression `(a % b > 0)`

evaluates to `True`

if `b`

is not a divisor of `a`

, otherwise it evaluates to `False`

. As the Boolean `True`

is represented by the integer value 1 in Python and Boolean `False`

by the integer value 0 in Python, the expression increments only if `b`

is not a divisor of `a`

.

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While working as a researcher in distributed systems, Dr. Christian Mayer found his love for teaching computer science students.

To help students reach higher levels of Python success, he founded the programming education website Finxter.com. He’s author of the popular programming book Python One-Liners (NoStarch 2020), coauthor of the Coffee Break Python series of self-published books, computer science enthusiast, freelancer, and owner of one of the top 10 largest Python blogs worldwide.

His passions are writing, reading, and coding. But his greatest passion is to serve aspiring coders through Finxter and help them to boost their skills. You can join his free email academy here.