Celsius to Fahrenheit
v1celsiusfahrenheitHow it is worked out
Convert a temperature from degrees Celsius to Fahrenheit, such as 25 °C which is 77 °F.
The two scales differ in two ways: where they put zero and how big a degree is. So the conversion multiplies by 9/5, since one Celsius degree is 1.8 Fahrenheit, and then adds 32, which is where Fahrenheit puts the freezing point of water.
The expression that runs
celsius * 9 / 5 + 32The fields arrive with an example filled in: put your own numbers in and run it again. You can also edit the formula to fit your case.
What if the formula were yours?
This calculator is not hand-written: it is an Axioma formula. Open it in the editor to see how it is built, adapt it to your case and create the ones you need.
Why it multiplies by 9/5 and adds 32
Between freezing and boiling there are 100 Celsius degrees and 180 Fahrenheit ones, so each Celsius degree is worth 180/100, which is 1.8. That is the 9/5 factor.
The 32 corrects the origin: zero Celsius is the freezing point of water, while Fahrenheit set its zero far below that. Without it, 0 °C would come out as 0 °F, which is around eighteen degrees below freezing.
Reference points for doing it in your head
Zero is 32 °F, ten is 50, twenty is 68, thirty is 86 and forty is 104. Body temperature, 37 °C, is 98.6 °F, which is the figure used in countries that measure in Fahrenheit.
A reasonable shortcut: double the Celsius and add 30. That gives 80 instead of 77 for 25 degrees, a three degree error, which is close enough to decide whether to take a coat.
The other direction, and the point where they meet
Going from Fahrenheit to Celsius reverses both steps and their order: subtract 32 first and then multiply by 5/9. From 77 °F you land back on exactly the 25 °C you started from.
There is exactly one temperature where both scales agree: forty degrees below zero. It is the only solution to the equation, which is why minus 40 is written the same way in both.
Frequently asked questions
- What is 25 degrees Celsius in Fahrenheit?
- It is 77 °F. The arithmetic is 25 times 1.8, which is 45, plus the 32 that separates the two zero points. It is a warm day in either scale.
- How do I go from Fahrenheit to Celsius?
- Subtract 32 and multiply by 5/9. It is the same formula rearranged, and you can write it in the editor starting from this one.
- Why is a fever 98.6 °F?
- Because it matches the 37 °C taken as reference body temperature. The decimal appears precisely because of the conversion.