🌡️ Temperature Converter
Type in any scale and the other two update instantly. Three-way, live, no buttons needed.
All Three Scales
How to Use This Converter
This converter has three inputs instead of the usual from/to pair. Type a temperature into whichever scale you have, and the other two fill in by themselves.
Type a temperature into the Celsius, Fahrenheit, or Kelvin box. Decimals and negatives work fine.
The other two boxes update instantly as you type. No convert button needed.
Editing a different box takes over: the newest edit always drives the other two.
Clear wipes all three boxes and the result card. Type again to restart.
Exact Conversion Formulas
Celsius and Fahrenheit differ in two ways: the size of a degree (a Fahrenheit degree is 5/9 the size of a Celsius degree) and the zero point (Fahrenheit puts freezing at 32). That is why the formula needs both the multiply and the offset. Kelvin shares the Celsius degree size and only shifts the zero to absolute zero, 273.15 degrees lower. For quick mental math: double the Celsius and add 30 to estimate Fahrenheit (100 C -> 230 F vs the true 212 F), and subtract 30 then halve for the reverse.
Worked Example
A recipe says bake at 200 C and your American oven shows Fahrenheit. Type 200 into Celsius: 200 x 9/5 + 32 = 392 F, and 200 + 273.15 = 473.15 K. A winter forecast of 20 F in Celsius: (20 - 32) x 5/9 = -6.67 C, a properly cold day. And a chemistry problem asking for 310.15 K in familiar units: 310.15 - 273.15 = 37 C, and 37 x 9/5 + 32 = 98.6 F, human body temperature.
Handy Reference Temperatures
Where This Comes Up
Cooking is the everyday battleground: European ovens and recipes use Celsius while American ones use Fahrenheit, and getting it wrong ruins dinner. Weather means translating forecasts when traveling or reading international news. Science classes and lab work run on Celsius and Kelvin, and Kelvin appears in color temperature for photography and lighting too (a 5600 K light is daylight-balanced). Engineering specs, aquarium keeping, and homebrewing all bounce between scales depending on who wrote the guide.
Frequently Asked Questions
What is 0 degrees Celsius in Fahrenheit?
32 degrees Fahrenheit. Water freezes at 0 C (32 F) and boils at 100 C (212 F) at sea level. In Kelvin that is 273.15 K and 373.15 K. These three points are the fastest way to sanity-check any conversion.
What is the formula for Celsius to Fahrenheit?
Multiply by 9/5 and add 32: F = C x 9/5 + 32. Going back: C = (F - 32) x 5/9. Kelvin adds 273.15: K = C + 273.15. These are exact definitions, so this converter rounds nothing until the final display.
At what temperature are Celsius and Fahrenheit the same?
Minus 40. -40 C equals -40 F exactly, the one point where the two scales cross. Below that, Fahrenheit reads lower (more negative) than Celsius; above it, Fahrenheit reads higher.
What is 98.6 F in Celsius?
37 C exactly: (98.6 - 32) x 5/9 = 37. That is normal human body temperature, and it is why 37 C is the reference point in medicine worldwide. In Kelvin it is 310.15 K.
Why do scientists use Kelvin instead of Celsius?
Kelvin starts at absolute zero (0 K = -273.15 C), the coldest anything can be, so there are no negative values to handle in equations like the ideal gas law. The size of one kelvin equals one degree Celsius, so only the zero point differs.