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Celsius to Fahrenheit

Convert °C to °F, with kelvin alongside.

Inputs
°C

The number of celsius to convert.

Fahrenheit
68°F
In kelvin
293.15K
0 °C
32°F
20 °C
68°F
37 °C
98.6°F
100 °C
212°F
°F = (°C × 9/5) + 32

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Multiply Celsius by 1.8 and add 32. Unlike most conversions this needs an offset as well as a factor, because the two scales put their zero in different places — 0 °C is 32 °F.

How to use Celsius to Fahrenheit

  1. Enter the temperature in Celsius. Negative values are fine.
  2. Read the Fahrenheit. To one decimal, with kelvin underneath for scientific use.

About converting Celsius to Fahrenheit

The two scales exist because they were built for different reference points by people with different aims. Fahrenheit, proposed in 1724, anchored zero to the coldest temperature Daniel Fahrenheit could reliably reproduce — a brine of ice, water and ammonium chloride — and set human body temperature near 96 on the original scale. Celsius, twenty years later, used two points that anyone can reproduce anywhere: the freezing and boiling points of water at standard pressure, giving a scale where the useful range of weather runs conveniently from about −20 to 40. That reproducibility is why science and almost every country adopted it. Two things are worth knowing when converting. Temperature differences do not convert the same way as temperatures: a rise of 10 °C is a rise of 18 °F, not 50, because the offset applies to points on the scale and not to intervals between them. And the famous 98.6 °F for body temperature is false precision — it is a conversion of a rounded 37 °C from a study in 1868, and modern measurements put the average nearer 36.6 °C. Neither scale is used at all in the physics of low temperatures, where kelvin starts at absolute zero and has no negative values.

Frequently asked questions

What is the quick mental conversion?
Double it and add 30. 20 °C becomes about 70 °F against the true 68; 30 °C becomes about 90 against 86. It drifts at the extremes but is accurate enough for deciding what to wear.
Why is there an offset rather than just a multiplier?
Because the scales disagree about where zero is. Celsius sets zero at the freezing point of water; Fahrenheit sets it at the freezing point of a brine solution, roughly −17.8 °C. The 32 accounts for that gap.
Is there a temperature where both scales read the same?
Yes, −40. It is the one point where the two lines cross, which is why −40 °C and −40 °F need no conversion and why that figure appears so often in cold-weather specifications.
What is normal body temperature in Fahrenheit?
37 °C is 98.6 °F. That familiar figure is an artefact of conversion: the original nineteenth-century measurement was 37 °C to the nearest degree, and converting it produced a spurious decimal that has been quoted as precision ever since.

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