Celsius to Kelvin (°C to K) Converter

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Celsius to Kelvin — Formula & Reference

Kelvin (K) is the SI base unit of temperature, used primarily in science and engineering. 0 K is absolute zero, the lowest theoretically possible temperature. The conversion from Celsius is simply an offset.

Formula

Reference Values

Related Temperature Converters

Why Kelvin Starts at Absolute Zero

The Kelvin scale is the SI temperature scale for science because it starts at absolute zero — the coldest possible temperature, where all thermal motion stops (−273.15 °C). Unlike Celsius or Fahrenheit, Kelvin has no negative values, making equations involving temperature ratios straightforward. For example, the ideal gas law PV = nRT requires temperature in Kelvin. Room temperature (~22 °C) is 295.15 K. The formula is simple: K = °C + 273.15.

Converting Celsius to Kelvin

The Kelvin scale is the SI base unit for thermodynamic temperature. The conversion from Celsius to Kelvin is simply K = °C + 273.15. The Kelvin scale has the same degree size as Celsius but starts at absolute zero (−273.15°C), the theoretically lowest possible temperature where molecular motion stops. There are no negative temperatures on the Kelvin scale. 0 K = −273.15°C = −459.67°F. The boiling point of water at sea level is 373.15 K.

Kelvin is used in science, engineering, and industry: gas laws (PV = nRT requires Kelvin), blackbody radiation (Wien's law uses Kelvin), color temperature of light sources (3000 K = warm white, 6500 K = daylight), and astrophysics (surface temperature of the Sun ≈ 5778 K). The Celsius and Kelvin scales only differ by the 273.15 offset — an interval of 1°C equals an interval of 1 K.

Celsius to Kelvin Reference

Why Scientists Prefer Kelvin Over Celsius

Adding 273.15 to a Celsius temperature converts it to Kelvin, the SI thermodynamic temperature unit. Kelvin is mandatory in gas law calculations because all temperature ratios must be positive: doubling the Kelvin temperature genuinely doubles the average kinetic energy of gas molecules, while doubling the Celsius temperature has no consistent physical meaning. The Boltzmann constant, Stefan-Boltzmann constant, and Planck’s law all use Kelvin. In chemistry, equilibrium constants and reaction rates depend exponentially on absolute temperature (the Arrhenius equation uses T in Kelvin). Cryogenics and superconductor research work in Kelvin because meaningful temperature differences are fractions of a kelvin near absolute zero, where negative Celsius values would be cumbersome. Converting Celsius to Kelvin is the first step before any thermodynamic or kinetic calculation requiring the absolute temperature scale.

Celsius to Kelvin Reference Table