How the conversion works
Temperature scales differ in two ways at once: where they place zero and how big each degree is. That is why converting is not a single multiplication like it is for length or weight.
To keep things consistent the tool routes everything through Celsius. It first turns your input into Celsius, then converts that to the unit you asked for.
- Fahrenheit: degrees Celsius times 1.8, then add 32.
- Kelvin: degrees Celsius plus 273.15.
Reading the result
The answer is shown in the unit you selected. A few anchor points help sanity-check it: water freezes at 0 C, 32 F and 273.15 K, and boils at 100 C, 212 F and 373.15 K.
Practical tips
Kelvin has no negative values in normal use because it starts at absolute zero, the coldest possible temperature. A negative Kelvin result usually means the input was wrong.
- For a quick mental estimate, double Celsius and add 30 to approximate Fahrenheit.
- Body temperature near 37 C is about 98.6 F.
Common mistakes
A frequent error is forgetting the offset and only scaling by 1.8, which is wrong for any non-zero temperature. The constant 32 (or 273.15 for Kelvin) must be included.
Check that the from and to units are not the same, or the value will simply pass through unchanged.
Formula
°F = °C·1.8 + 32; K = °C + 273.15Frequently asked questions
- How do I convert Celsius to Fahrenheit?
- Multiply by 1.8 and add 32. Going the other way, subtract 32 first and then divide by 1.8.
- At what temperature do Celsius and Fahrenheit meet?
- −40. It is the one point where the two scales read the same number.
- Why does Kelvin have no degree sign?
- Kelvin is an absolute scale starting at absolute zero, not a scale of degrees above an arbitrary point, so the unit is written simply as K. It is Celsius plus 273.15.