Round a float to the nearest 0.5 in Python

Borislav Hadzhiev

Last updated: Jul 12, 2022

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- Round a float to the nearest 0.5 in Python
- Round a float Up to the nearest 0.5 in Python
- Round a float Down to the nearest 0.5 in Python

**To round a float to the nearest 0.5:**

- Call the
`round()`

function passing it the number multiplied by`2`

. - Divide the result by
`2`

. - The result of the calculation is the number rounded to the nearest
`0.5`

.

main.py

`import math # ✅ Round number to nearest 0.5 def round_to_nearest_half_int(num): return round(num * 2) / 2 print(round_to_nearest_half_int(3.1)) # 👉️ 3.0 print(round_to_nearest_half_int(3.7)) # 👉️ 3.5 # -------------------------------------- # ✅ Round number UP to nearest 0.5 def round_up_to_nearest_half_int(num): return math.ceil(num * 2) / 2 print(round_up_to_nearest_half_int(3.1)) # 👉️ 3.5 print(round_up_to_nearest_half_int(3.7)) # 👉️ 4.0 # -------------------------------------- # ✅ Round number DOWN to nearest 0.5 def round_down_to_nearest_half_int(num): return math.floor(num * 2) / 2 print(round_down_to_nearest_half_int(3.9)) # 👉️ 3.5 print(round_down_to_nearest_half_int(3.4)) # 👉️ 3.0`

We used the `round()`

function to round a number to the nearest 0.5.

When passed a single argument, the round function rounds to the nearest integer.

main.py

`print(round(7.4)) # 👉️ 7 print(round(7.6)) # 👉️ 8`

Here is a step-by-step example of rounding a number up to the nearest `0.5`

.

main.py

`print(3.1 * 2) # 👉️ 6.2 print(3.7 * 2) # 👉️ 7.4 print(round(3.1 * 2)) # 👉️ 6 print(round(3.7 * 2)) # 👉️ 7 print(round(3.1 * 2) / 2) # 👉️ 3.0 print(round(3.7 * 2) / 2) # 👉️ 3.5`

This is a two step process:

- Multiply the number by
`2`

and round the result to the nearest integer. - Divide the result by
`2`

to get the number rounded to the nearest`0.5`

.

**To round a float up to the nearest 0.5:**

- Call the
`math.ceil()`

method passing it the number multiplied by`2`

. - Divide the result by
`2`

. - The result of the calculation is the number rounded up to the nearest
`0.5`

.

main.py

`import math def round_up_to_nearest_half_int(num): return math.ceil(num * 2) / 2 print(round_up_to_nearest_half_int(3.1)) # 👉️ 3.5 print(round_up_to_nearest_half_int(3.7)) # 👉️ 4.0 print(round_up_to_nearest_half_int(16.2)) # 👉️ 16.5`

The math.ceil method returns the smallest integer greater than or equal to the provided number.

main.py

`import math print(math.ceil(3.1)) # 👉️ 4 print(math.ceil(3.9)) # 👉️ 4`

If the passed in number has a fractional part, the

`math.ceil`

method rounds the number up.Here is a step-by-step example of rounding a number up to the nearest `0.5`

.

main.py

`import math print(6.1 * 2) # 👉️ 12.2 print(6.6 * 2) # 👉️ 13.2 print(math.ceil(6.1 * 2)) # 👉️ 13 print(math.ceil(6.6 * 2)) # 👉️ 14 print(math.ceil(6.1 * 2) / 2) # 👉️ 6.5 print(math.ceil(6.6 * 2) / 2) # 👉️ 7.0`

This is a two step process:

- Multiply the number by
`2`

and round the result up to the nearest integer. - Divide the result by
`2`

to get the number rounded up to the nearest`0.5`

.

**To round a number down to the nearest 0.5:**

- Call the
`math.floor()`

method passing it the number multiplied by`2`

. - Divide the result by
`2`

. - The result of the calculation is the number rounded down to the nearest
`0.5`

.

main.py

`import math def round_down_to_nearest_half_int(num): return math.floor(num * 2) / 2 print(round_down_to_nearest_half_int(3.9)) # 👉️ 3.5 print(round_down_to_nearest_half_int(3.4)) # 👉️ 3.0`

The math.floor method returns the largest integer less than or equal to the provided number.

main.py

`import math print(math.floor(3.9)) # 👉️ 3 print(math.floor(3.1)) # 👉️ 3`

If the passed in number has a fractional part, the

`math.floor`

method rounds the number down.Here is a step-by-step example of rounding a number down to the nearest `0.5`

.

main.py

`import math print(5.9 * 2) # 👉️ 11.8 print(5.1 * 2) # 👉️ 10.2 print(math.floor(5.9 * 2)) # 👉️ 11 print(math.floor(5.1 * 2)) # 👉️ 10 print(math.floor(5.9 * 2) / 2) # 👉️ 5.5 print(math.floor(5.1 * 2) / 2) # 👉️ 5.0`

This is a two step process:

- Multiply the number by
`2`

and round the result down to the nearest integer. - Divide the result by
`2`

to get the number rounded down to the nearest`0.5`

.