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Temperature
Celsius to Kelvin
Convert Celsius (°C) to Kelvin (K). Type a value below to see the result update instantly. Reference table and formula included.
Calculator
1 °C = 274.15 K
Celsius to Kelvin Conversion Table
Common values, ready to copy:
| Celsius | Kelvin |
|---|---|
| 1 °C | 274.15 K |
| 2 °C | 275.15 K |
| 5 °C | 278.15 K |
| 10 °C | 283.15 K |
| 25 °C | 298.15 K |
| 50 °C | 323.15 K |
| 100 °C | 373.15 K |
| 1,000 °C | 1273.15 K |
Formula
K = °C + 273.15
Temperature scales differ in both unit size and zero point, so the conversion involves both a multiplier and an offset. Celsius and Kelvin share the same degree size; Fahrenheit's degree is 5/9 the size of a Celsius/Kelvin degree.
Where Kelvin comes from
William Thomson, later ennobled as Lord Kelvin, proposed the absolute thermodynamic temperature scale in 1848. The motivation was a physical fact, not human convenience: there is a coldest possible temperature, called absolute zero, at which all thermal motion stops. Kelvin set zero on his scale to that point — −273.15°C in modern values — and kept the degree size identical to the Celsius degree.
Because Kelvin uses the same degree size as Celsius, the conversion is a pure additive shift. There's no multiplier, no slope adjustment. You just add or subtract 273.15. Note that "degrees Kelvin" is the wrong term — by convention since 1967, the SI unit is just "kelvin," lowercase, and the symbol K stands alone without a degree sign.
The formula
K = °C + 273.15
Memorizable in two seconds. Water freezes at 273.15 K, boils at 373.15 K, and human body temperature is about 310 K. Room temperature is around 293 K. Absolute zero is 0 K.
When you'd use this conversion
Kelvin is the SI base unit of temperature, so it appears in any equation derived from physical constants: the ideal gas law (PV = nRT), Stefan-Boltzmann radiation, blackbody curves, and almost every thermodynamics calculation. Chemistry uses Kelvin for gas-phase reaction kinetics, vapor pressure calculations, and anything involving the Arrhenius equation.
Outside physics and chemistry, you encounter Kelvin in two surprising places. First, color temperature of light: warm yellow incandescent bulbs are around 2700 K, cool daylight is around 5500 K, overcast sky is 6500 K. Photographers and lighting designers use these values constantly. Second, in astronomy and astrophysics, where surface temperatures of stars range from about 3,000 K (red dwarfs) to over 50,000 K (blue supergiants).
Common mistakes
The most common mistake is treating Kelvin like it's another version of Fahrenheit — multiplying or scaling when you should just add. The relationship is purely additive: K and °C have the same degree size, so a 10-degree temperature change is 10 K and 10°C, identically.
Another subtle mistake is rounding 273.15 to 273. For weather or rough conversion the rounding is fine. For ideal-gas or thermodynamics work, that 0.15 K matters; pressure and volume calculations are sensitive to small absolute-temperature differences, especially near the freezing point of water.