In every science class, you must know how to use and interpret the Celsius temperature scale. But this can be difficult for students who are used to using Fahrenheit instead. How do you convert Celsius to Fahrenheit? What about Fahrenheit to Celsius?
We answer these questions below, giving you the mathematical formulas for converting between these two temperature units, a handy conversion chart, and a quick conversion trick you can use without having to grab a calculator.
Celsius vs Fahrenheit: Key Differences
Before we explain how to convert Celsius to Fahrenheit (and Fahrenheit to Celsius), let’s review the main differences between the two temperature scales.
Celsius (written as °C and also called Centigrade) is the most common temperature scale in the world, used by all but five countries. It’s part of the International System of Units (SI), or what you might know as the metric system, which is typically used in science classes (think centimeters, meters, kilograms, milliliters, etc.) and in science as a whole.
By contrast, Fahrenheit (written as °F) is only used officially by five countries in the world:
 United States
 Belize
 Cayman Islands
 Palau
 Bahamas
Fahrenheit is not part of the metric system; rather, it’s part of the Imperial system, which includes forms of measurements such as inches, feet, pounds, gallons, etc. Moreover, unlike Celsius, it is not typically used in science.
Celsius to Fahrenheit Formula
Unfortunately, converting from Celsius to Fahrenheit isn’t easy to do quickly or in your head. Here are the formulas used to convert Celsius to Fahrenheit and Fahrenheit to Celsius. These formulas will give you the exact conversion from one unit of temperature to the other:
Celsius to Fahrenheit Formula: (°C * 1.8) + 32 = °F
Fahrenheit to Celsius Formula: (°F  32) / 1.8 = °C
For example, say the temperature outside is 18 °C and you want to know what this would equal in Fahrenheit. Here’s how your equation would look once you plug in 18 for °C:
(18 * 1.8) + 32
(32.4) + 32
=64.4 °F
Here’s another example if you want to convert Fahrenheit to Celsius: say you’re feeling ill and your body temperature is 101.3 °F. To find out what this equals in Celsius, simply plug 101.3 into the °F part in the second equation written above:
(101.3  32) / 1.8
(69.3) / 1.8
=38.5 °C
As you can see, these conversions aren’t particularly hard to carry out, but they do take some time and aren’t the easiest to do without a calculator on hand.
Luckily, there’s a shortcut. By memorizing some of the most common temperatures that come up in daily life, you should have no problem being able to convert from Celsius to Fahrenheit and vice versa. We’ll take a look at how to do this next.
It's gettin' hot in here.
Celsius to Fahrenheit Conversion Chart
Below is a conversion chart listing some of the most commonly used temperatures in everyday life when converting from Celsius to Fahrenheit. Memorize these and you’re sure to have an easier time converting from Celsius to Fahrenheit (and vice versa) fast.
Note: I’ve bolded all temperatures that don’t apply to weather but are still important to know, especially for science class.

Temperature in Celsius (°C)

Temperature in Fahrenheit (°F)

Boiling Point of Water

100

212

Extremely Hot Day

40

104

Body Temperature

37

98.6

Hot Day

30

86

Room Temperature

20

68

Chilly Day

10

50

Freezing Point of Water

0

32

Very Cold Day

10

14

Extremely Cold Day

20

4

Parity*

40

40

Source: NIST.gov
*The point at which the two temperature units are equivalent (40 °C = 40 °F).
As you can see from this chart, Fahrenheit temperatures are typically a lot higher than their equivalent Celsius temperatures are.
Also, notice how the difference between Celsius and Fahrenheit starts to get smaller the lower you go in temperature—until, that is, they're the exact same! As the chart indicates, 40 °C is the same temperature as 40 °F. This point is called parity, meaning the two scales use the same value to represent the same temperature. Unfortunately (or fortunately, since this is pretty cold!), you likely won’t come across this temperature in your daily life.
Note that parity only happens at 40°. The lower you go after parity (i.e., the further you go into the negatives), the bigger the difference starts to become again between Celsius and Fahrenheit.
How to Convert Celsius to Fahrenheit: Quick Trick
If you find yourself needing to quickly convert Celsius to Fahrenheit, here is a simple trick you can use: multiply the temperature in degrees Celsius by 2, and then add 30 to get the (estimated) temperature in degrees Fahrenheit. This rule of thumb is really useful and also pretty accurate for most weatherrelated temperatures.
For example, if the temperature outside is 15 °C, this would come out to around 60 °F:
(15 * 2) + 30
(30) + 30
= 60 °F (In reality, 15 °C is equivalent to 59 °F—that’s pretty close!)
Of course, expect the actual temperature to be a few degrees off, but for the most part, this is a reliable and easy way to convert temperatures in your head fast.
If you want to convert Fahrenheit to Celsius, do the opposite: subtract 30 from the temperature in degrees Fahrenheit, and then divide by 2 to get the temperature in degrees Celsius.
For example, if the temperature outside is 84 °F, this would be roughly equal to 27 °C:
(84  30) / 2
54 / 2
= 27 °C (In reality, 84 °F is equivalent to 28.89 °C—again, that’s a pretty close estimate!).
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Hannah received her MA in Japanese Studies from the University of Michigan and holds a bachelor's degree from the University of Southern California. From 2013 to 2015, she taught English in Japan via the JET Program. She is passionate about education, writing, and travel.