Convert Kelvin (K) to Celsius (°C) instantly.
About these units
Kelvin (K)
The kelvin is the base unit of temperature in the International System of Units (SI) and is unique among temperature scales because it begins at absolute zero, the theoretical point where all classical molecular motion ceases. This gives the kelvin an absolute physical foundation that other temperature scales lack. Instead of being tied to the properties of water or human experience, the kelvin reflects universal thermodynamic behavior, making it indispensable for physics, chemistry, engineering, and cosmology. One of the kelvin's strengths is that temperature differences measured in kelvins are identical to those measured in degrees Celsius, simplifying conversions in scientific work. The kelvin scale is critical for understanding entropy, thermal energy, and statistical mechanics, where temperature represents average kinetic energy of particles rather than subjective sensation. Modern definitions anchor the kelvin to a fixed numerical value of the Boltzmann constant, connecting macroscopic temperature directly to microscopic energy. This reformulation, adopted in 2019, ensures that the kelvin remains precise and universally stable across laboratories worldwide, independent of any specific material reference point. As such, the kelvin is not merely a unit of temperature—it is a gateway to the deeper physical meaning of heat and energy.
Celsius (°C)
The Celsius scale is one of the world's most widely used temperature scales, rooted in human experience and environmental observation. Defined so that water freezes at 0°C and boils at 100°C under standard atmospheric pressure, the scale provides intuitive benchmarks that align closely with everyday life, weather reporting, cooking, and basic heating or cooling applications. In scientific work, the Celsius scale aligns neatly with the kelvin: T(K) = T(°C) + 273.15, which preserves temperature intervals and ensures compatibility with thermodynamic equations. This makes Celsius suitable for most laboratory temperature measurements while maintaining convenience for ordinary use. Historically, the scale was reversed—originally, 0°C represented water's boiling point and 100°C its freezing point. It was later inverted to match modern intuitive expectations and became standardized internationally. Today, Celsius serves as a bridge between everyday perception and scientific rigor, striking a balance between practicality and precision.