Temperature Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/3/2026
To convert Celsius to Fahrenheit, multiply by 9/5 and add 32 (0 °C = 32 °F). To convert to Kelvin, add 273.15 to the Celsius value (0 °C = 273.15 K).
Explanation
The three temperature scales have different origins: Celsius sets 0° at water's freezing point, Fahrenheit (still used in the United States) sets 32° at that same point with finer gradations, and Kelvin, the international scientific unit, starts at absolute zero (-273.15 °C), the lowest temperature theoretically achievable. That's why the Celsius-to-Kelvin conversion is a simple addition (same degree size, different origin), while the Celsius-to-Fahrenheit conversion also involves a scale change (multiplying by 9/5). This calculator accepts input in any of the three units and instantly shows the other two.
Example: converting 20 °C
Inputs
Value: 20. Input unit: Celsius.
Calculation
In Fahrenheit: 20 × 9/5 + 32 = 36 + 32 = 68 °F. In Kelvin: 20 + 273.15 = 293.15 K.
Result
20 °C equals 68 °F and 293.15 K.
Frequently asked questions
Why doesn't Kelvin use the degree symbol (°)?
Because Kelvin is an absolute thermodynamic temperature unit, not an arbitrary graduated scale: by convention of the International System of Units, it's written "273.15 K", not "273.15 °K".
Is there a temperature where Celsius and Fahrenheit coincide?
Yes: at -40°, the two scales give the same value (-40 °C = -40 °F). It's the only point where the two scales cross.
Is absolute zero (0 K) achievable in practice?
No: the third law of thermodynamics establishes that it's physically impossible to reach absolute zero exactly, only to approach it. The most advanced physics labs reach temperatures a few billionths of a Kelvin above zero.