How to Convert Celsius and Fahrenheit

Most countries use Celsius so it's important to know both

Most countries around the world measure their weather and temperatures using the relatively simple Celsius scale. But the United States is one of the five remaining countries that use the Fahrenheit scale, so it's important for Americans to know how to convert one to the other, especially when traveling or doing scientific research. 

Celsius Fahrenheit Conversion Formulas

To convert a temperature from Celsius to Fahrenheit, you will take the temperature in Celsius and multiply it by 1.8, then add 32 degrees.

So if your Celsius temperature is 50 degrees, the corresponding Fahrenheit temperature is 122 degrees:

(50 degrees Celsius x 1.8) + 32 = 122 degrees Fahrenheit

If you need to convert a temperature in Fahrenheit, simply reverse the process: subtract 32, then divide by 1.8. So 122 degrees Fahrenheit is still 50 degrees Celsius:

(122 degrees Fahrenheit - 32)  ÷ 1.8 = 50 degrees Celsius

It's Not Just About Conversions

While it's useful to know how to convert Celsius to Fahrenheit and vice versa, it's also important to understand the differences between the two scales. First, it's important to clarify the difference between Celsius and centigrade, since they're not quite the same thing. 

A third international unit of temperature measurement, Kelvin, is widely used in scientific applications. But for everyday and household temperatures (and your local meteorologist's weather report), you're most likely to use Fahrenheit in the U.S. and Celsius most other places around the world.

 

Difference Between Celsius and Centigrade

Some people use the terms Celsius and centigrade interchangeably, but it's not completely accurate to do so. The Celsius scale is a type of centigrade scale, meaning its endpoints are separated by 100 degrees. The word is derived from the Latin words centum, which means hundred, and gradus, which means scales or steps.

Put simply, Celsius is the proper name of a centigrade scale of temperature.

As devised by Swedish astronomy professor Anders Celsius, this particular centigrade scale had 100 degrees occurring at the freezing point of water and 0 degrees as water's boiling point. This was reversed after his death by fellow Swede and botanist Carlous Linneaus to be more easily understood. The centigrade scale Celsius created was renamed for him after it was redefined to be more precise by the General Conference of Weights and Measures in the 1950s. 

There is one  point on both scales where Fahrenheit and Celsius temperatures match, which is minus 40 degrees Celsius and minus 40 degrees Fahrenheit. 

Invention of the Fahrenheit Temperature Scale

The first mercury thermometer was invented by German scientist Daniel Fahrenheit in 1714. His scale divides the freezing and boiling points of water into 180 degrees, with 32 degrees as water's freezing point, and 212 as its boiling point.

On Fahrenheit's scale, 0 degrees was determined as the temperature of a brine solution.

He based the scale on the average temperature of the human body, which he originally calculated at 100 degrees (it's since been adjusted to 98.6 degrees).

Fahrenheit was the standard unit of measure in most countries until the 1960s and 1970s, when it was replaced in most countries with the Celsius scale in a widespread conversion to the more useful metric system.  But in addition to the U.S. and its territories, Fahrenheit is still used in the Bahamas, Belize, and the Cayman Islands for most temperature measurements.