What is the formula to convert Celsius to Fahrenheit in Python?

f = c * 9 / 5 + 32. For 100 °C it gives 212.0 °F, and for 0 °C it gives 32.0 °F.

How do I convert Fahrenheit to Celsius?

c = (f - 32) * 5 / 9. Subtract 32 first — that is what the brackets are for — then multiply by 5 / 9. For 212 °F it gives 100.0 °C.

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Celsius to Fahrenheit in Python

easyInput and operatorsPython

A formula program that also teaches something important about Python 3: the / operator always gives a decimal answer.

Quick answer

The formula is F = C × 9 / 5 + 32, and the reverse is C = (F − 32) × 5 / 9. In Python: f = c * 9 / 5 + 32. So 0 °C is 32.0 °F, 37 °C (body temperature) is 98.6 °F and 100 °C is 212.0 °F.

The question

Read a temperature in Celsius (an integer) and print it in Fahrenheit using F = C × 9 / 5 + 32.

The code

program.py

c = int(input())
f = c * 9 / 5 + 32
print("Fahrenheit =", f)

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Input

Output

Fahrenheit = 158.0

How it works

1Read the temperature in Celsius.
2Apply F = C × 9 / 5 + 32. Multiplication and division happen before addition.
3Because / produces a float, a whole answer such as 212 prints as 212.0.

The formula on common temperatures

c	c * 9 / 5 + 32	Fahrenheit
0	0 * 9 / 5 + 32	32.0
37	37 * 9 / 5 + 32	98.6
100	100 * 9 / 5 + 32	212.0
-40	-40 * 9 / 5 + 32	-40.0

−40 is the one temperature that is the same in both scales.

Common mistakes

Writing C * (9 / 5 + 32) — the brackets change the order and the answer is wrong.
Using // (floor division), which throws away the decimal part.

Fahrenheit to Celsius (the reverse)

Turn the formula around: subtract 32 first, then multiply by 5 / 9. The brackets make the subtraction happen first.

program.py

f = float(input())
c = (f - 32) * 5 / 9
print("Celsius =", c)

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Input

Output

Celsius = 100.0

Print a Celsius to Fahrenheit table using a loop

range(0, 101, 20) gives 0, 20, 40 … 100, and the same formula is applied to each value.

program.py

for c in range(0, 101, 20):
    print(c, "C =", c * 9 / 5 + 32, "F")

Try it Yourself »

Input

(no input)

Output

0 C = 32.0 F
20 C = 68.0 F
40 C = 104.0 F
60 C = 140.0 F
80 C = 176.0 F
100 C = 212.0 F

Questions students ask

What is the formula to convert Celsius to Fahrenheit in Python?: f = c * 9 / 5 + 32. For 100 °C it gives 212.0 °F, and for 0 °C it gives 32.0 °F.
How do I convert Fahrenheit to Celsius?: c = (f - 32) * 5 / 9. Subtract 32 first — that is what the brackets are for — then multiply by 5 / 9. For 212 °F it gives 100.0 °C.

Now solve a similar question yourself

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Practice questions

Preparing for NIELIT O Level?

This program is the kind asked in the M3 (Python) theory paper and the PR-3 practical exam.

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