Python `round()` Function Explained

The built-in round() function returns a rounded version of a number.

You can use it in two common ways:

round(number) rounds to the nearest whole number
round(number, digits) rounds to a chosen number of decimal places

This is useful when you want cleaner numeric output or when you need to limit decimal places in a result.

Quick example

print(round(3.14159))
print(round(3.14159, 2))

Output:

3
3.14

Use round(number) to round to the nearest whole number, or round(number, digits) to keep a set number of decimal places.

What `round()` does

round() is a built-in Python function
It returns a rounded version of a number
With one argument, it rounds to the nearest integer
With two arguments, it rounds to a chosen number of decimal places

You do not need to import anything to use it.

Basic syntax

The syntax is:

round(number[, ndigits])

number is the value to round
ndigits is optional
ndigits can be positive, zero, or negative

Basic examples:

print(round(7.8))
print(round(7.8, 1))
print(round(1234, -2))

Output:

8
7.8
1200

If you are still getting used to Python number types, see Python numbers explained: int, float, complex.

Using `round()` with one argument

When you pass only one argument, Python rounds to the nearest whole number.

print(round(4.2))
print(round(4.8))

Output:

4
5

With a normal float, the result is usually an integer:

result = round(10.2)
print(result)
print(type(result))

Output:

10
<class 'int'>

If you need to convert values directly to integers without rounding rules, compare this with Python int() function explained.

Using `round()` with decimal places

You can pass a second argument to control how many decimal places to keep.

print(round(3.14159, 2))
print(round(3.14159, 3))

Output:

3.14
3.142

This is helpful when you want a simpler numeric value for calculations or reporting.

price = 19.9876
rounded_price = round(price, 2)

print(price)
print(rounded_price)

Output:

19.9876
19.99

If you need to convert text such as "3.14159" before rounding, see how to convert a string to float in Python or Python float() function explained.

Using negative `ndigits`

A negative ndigits value rounds to tens, hundreds, or larger place values.

print(round(1234, -1))
print(round(1234, -2))
print(round(1234, -3))

Output:

1230
1200
1000

How this works:

-1 rounds to the nearest 10
-2 rounds to the nearest 100
-3 rounds to the nearest 1000

This can be useful when you want less precise but easier-to-read numbers.

Important behavior beginners notice

Some results may look surprising with numbers ending in .5.

For example:

print(round(2.5))
print(round(3.5))

Output:

2
4

Python uses banker's rounding in tie cases. That means it rounds to the nearest even number in some .5 situations.

More examples:

print(round(1.5))
print(round(2.5))
print(round(3.5))
print(round(4.5))

Output:

This is normal Python behavior, not a bug.

So:

round(2.5) gives 2
round(3.5) gives 4

If you expected .5 to always round upward, this behavior can be confusing at first.

Return values

round() returns the rounded value.

It does not change the original variable unless you save the result.

value = 3.14159

print(value)
print(round(value, 2))
print(value)

Output:

3.14159
3.14
3.14159

If you want to keep the rounded value, assign it:

value = 3.14159
value = round(value, 2)

print(value)

Output:

3.14

When to use `round()`

Use round() when you want to:

Display simpler numeric output
Limit decimal places in calculations
Round values before reporting results
Prepare numbers for easier reading

For example:

distance = 12.67891
print(round(distance, 2))

Output:

12.68

Common mistakes

Here are some common beginner mistakes when using round().

Expecting `round()` to always round `.5` upward

This is one of the most common surprises.

print(round(2.5))
print(round(3.5))

Output:

2
4

Python may round tie values to the nearest even number.

Forgetting to save the returned value

round() returns a new value. It does not update the old one by itself.

value = 3.14159
round(value, 2)

print(value)

Output:

3.14159

To keep the rounded result:

value = round(value, 2)

Passing a string instead of a number

This will cause an error:

# print(round("3.14", 1))

You need to convert the string first:

text = "3.14"
number = float(text)

print(round(number, 1))

Output:

3.1

Confusing rounding a value with formatting text output

round() changes the numeric value it returns. It is not the same as formatting text for display.

If your data starts as text, convert it first with float() or int().

FAQ

Does `round()` always round `0.5` up?

No. In tie cases, Python may round to the nearest even number.

Does `round()` change the original number?

No. It returns a new value. You must assign it if you want to keep it.

Can `round()` round to tens or hundreds?

Yes. Use a negative ndigits value like -1 or -2.

Can I use `round()` on a string like `"3.14"`?

Not directly. Convert the string first with float() or int().

Python round() Function Explained

Python `round()` Function Explained