Depending on where you live in the world, you either use the Fahrenheit or the Celsius temperature scale. Converting between the two is easier than you may expect. A couple of simple formulas can help you estimate or exactly convert between the temperature scales.
If you're living in the United States, you're probably accustomed to reading temperatures in Fahrenheit. On a summer day with the sun beating down on you, it may feel like almost 100 degrees, while a winter day may feel closer to 40 degrees. Yet, if you were living in almost any other country in the world, you're likely used to reading temperatures in Celsius. In this case, 40 degrees describes a hot summer day, while zero degrees would be more typical of a winter day.
The Fahrenheit scale was created by Daniel Gabriel Fahrenheit in 1724. He originally created the scale to measure temperature using mercury thermometers, which he also invented. The Celsius scale was created by Anders Celsius in 1742. But when the scale was first introduced, Celsius used the reverse of today's scale. He labeled 0 as the boiling point of water and 100 as the freezing point. After Celsius' death, Swedish taxonomist Carl Linnaeus flipped the Celsius scale into what it is today, making 100 represent boiling temperature and 0 as the freezing point.
How to Convert Celsius to Fahrenheit Quickly
This formula will help you make a close estimate for a Fahrenheit temperature when you're converting from Celsius. This is a great formula to do quickly in your head. Simply multiply the Celsius temperature by 2 and add 30 to it:
(Celsius temp. x 2) + 30 = Fahrenheit temp.
Here's an example using 30 degrees C.
(30 x 2) + 30 = 90 degrees F.
This is pretty close to the 86 degrees F reading you'd get using the more precise method (explained later).
How to Convert Fahrenheit to Celsius Quickly
To do a rough approximation of Celsius using Fahrenheit, reverse the earlier formula. Subtract 30 from the Fahrenheit degrees, then divide your answer by 2.
(Fahrenheit temp. – 30) ÷ 2 = Celsius temp.
Let's say the Fahrenheit temperature is 80 degrees. The approximate Celsius temperature would be:
(80 – 30) ÷ 2 = 25 C
How to Convert Celsius to Fahrenheit (Exact Calculation)
If you're looking to get a more precise calculation, you can use this exact formula. You may want to have a calculator handy when you do this.
(Celsius temp. × 1.8) + 32 = Fahrenheit temp.
Begin the conversion by multiplying the temperature in Celsius by 1.8 (or 9/5), then add 32 to your answer to get the Fahrenheit reading.
Here's an example using 30 degrees Celsius.
(30 x 1.8) + 32 = 86 F
How to Convert Fahrenheit to Celsius (Exact Calculation)
When converting Fahrenheit to Celsius, you simply reverse the same equation above. Subtract 32 from the degrees in Fahrenheit, then divide your answer by 1.8.
(Fahrenheit temp. – 32) ÷ 1.8 = Celsius temp.
Here is the formula in action starting with 80 degrees F:
(80 – 32) ÷ 1.8 = 26.6 C (or round up to 27 C)