Temperature Converter
Convert a temperature between Celsius, Fahrenheit and kelvin. The scales have different zero points, so the page shows the exact formula it applied instead of a single multiplier.
The scales have different zero points: 0 °C, 32 °F and 273.15 K are all the same temperature, so there is no single conversion factor.
Formula and calculation
Worked example
Normal body temperature is 37 °C, which this converter reports as 98.6 °F. The arithmetic is °F = 37 × 9/5 + 32, and to go back the other way you would use °C = (98.6 - 32) × 5/9.
Why temperature is not a simple multiplication
Doubling a Celsius reading does not double the Fahrenheit reading, because the two scales start at different places: 0 °C is 32 °F, and 0 °F is -17.8 °C. Only intervals scale proportionally — a 10 °C rise is an 18 °F rise. That is why this page prints the formula it applied instead of one factor line, and why there is no single number you can memorise for the whole conversion. For science and engineering, work in kelvin: it counts from absolute zero, so it has no negative values and no offset, which makes multiplying and dividing temperatures meaningful.
What the results mean
- 100 °C =
- Your temperature converted to the target scale, exactly as entered - 37 °C becomes 98.6 °F, and 0 K is -273.15 °C.
- Formula applied
- The formula that was applied, with your number substituted, so you can check the arithmetic or repeat it on a calculator.
- Reverse formula
- The same conversion backwards, starting from the result, for getting to the original scale again.
Frequently asked questions
What is 100 degrees Fahrenheit in Celsius?
37.8 °C: subtract 32 and multiply by 5/9. The mental shortcut is to subtract 30 and halve the result, which gives roughly 35 °C — close enough for a weather forecast, not for anything that matters.
Why is 0 °C not the same as 0 °F?
Because the scales were built from different fixed points, so their zeros sit at different temperatures. 0 °C, the freezing point of water, is 32 °F, while 0 °F is about -17.8 °C. That offset is what breaks a simple multiplier.
What is 98.6 °F in Celsius?
Exactly 37 °C, the classic normal body temperature: (98.6 - 32) × 5/9 = 37. A reading of 100.4 °F is 38 °C, which is the usual threshold for a fever, and body temperature varies by about a degree over the day.
Is one kelvin the same as one degree Celsius?
Yes for a temperature difference: one kelvin is exactly one degree Celsius in size, and the two scales differ only by the 273.15 offset. Water boils at 100 °C, which is 373.15 K. Negative kelvin values are below absolute zero and are rejected here.