Temperature Converter
Convert temperature
Convert temperature Runs locally in your browser
About the
The Temperature Converter translates between Celsius, Fahrenheit and Kelvin, and unlike most unit conversions these three do not share a zero point, which is why you cannot simply multiply. Celsius and Fahrenheit differ by both a scale factor and an offset, and Kelvin is an absolute scale starting at absolute zero, so it has no negative values and no degree sign. The one number worth remembering is minus 40, the point at which the Celsius and Fahrenheit scales cross and give the same reading.
Where people use the
- Converting an oven temperature between a US and a European recipe.
- Reading a weather forecast in the scale you think in.
- Checking a scientific figure given in Kelvin.
- Working out whether a fever reading is concerning.
How to use the
- 1
Enter a value
Type any temperature, including decimals and negative numbers.
- 2
Choose the unit you are converting from
Celsius, Fahrenheit or Kelvin.
- 3
Choose the unit you want
The result updates immediately, so you can flip the direction without retyping.
- 4
Sanity check the result
Water freezes at 0 Celsius, 32 Fahrenheit and 273.15 Kelvin, and boils at 100 Celsius and 212 Fahrenheit. Those anchors catch a swapped unit instantly.
Tips and best practices
- Remember minus 40 as the crossover; it catches most unit mistakes.
- Use the freezing and boiling points of water as your sanity check.
- Do not add 32 when converting a temperature difference, only a reading.
Frequently asked questions
What are the formulas?
Fahrenheit equals Celsius times 9/5 plus 32. Celsius equals Fahrenheit minus 32, times 5/9. Kelvin equals Celsius plus 273.15. Everything else is a combination of those three.
At what temperature are Celsius and Fahrenheit equal?
Minus 40. Below that the Fahrenheit number is larger, above it the Celsius number is larger. It is the only point where the two scales agree.
Why does Kelvin have no degree symbol?
Because it is an absolute scale, not a degree of something. You write 273.15 K, not 273.15 degrees Kelvin. Absolute zero, 0 K, is the theoretical point at which molecular motion stops, roughly minus 273.15 Celsius.
Why is my conversion slightly off from another site?
Usually rounding. The conversion factor between Celsius and Fahrenheit is exact, 9/5, so any difference comes from how many decimal places were kept, not from the formula.
Can I convert a temperature difference rather than a reading?
Not with this tool, and the distinction matters. A change of 10 Celsius is a change of 18 Fahrenheit, with no 32 added, because the offset applies to readings, not to intervals.