Celsius to Kelvin: °C to K Converter
Convert Celsius to Kelvin (or any temperature scale) instantly. Add 273.15 to Celsius to get Kelvin. Used in science (chemistry, physics, astronomy), engineering (HVAC, cryogenics), and photography (color temperature). Enter any value in any scale below; the other scales update in real time.
°F = (0 × 9/5) + 32 = 32°F
Celsius to Kelvin reference table
| Celsius | Kelvin | Note |
|---|---|---|
| -273.15°C | 0 K | Absolute zero |
| -40°C | 233.15 K | Where C and F meet |
| -18°C | 255.15 K | Typical freezer |
| 0°C | 273.15 K | Water freezes |
| 20°C | 293.15 K | Room temperature |
| 37°C | 310.15 K | Body temperature |
| 100°C | 373.15 K | Water boils |
| 200°C | 473.15 K | Hot oven (medium) |
| 500°C | 773.15 K | Glass softens |
| 1538°C | 1811.15 K | Iron melts |
| 5505°C | 5778.15 K | Surface of the Sun |
About the Kelvin scale
The conversion
Kelvin and Celsius use the same degree size (a 1 K change equals a 1°C change). The only difference is where the zero point is: Celsius zero is at the freezing point of water; Kelvin zero is at absolute zero, the lowest theoretically possible temperature. To convert between them, add or subtract 273.15.
Lord Kelvin and the scale
The scale was proposed by William Thomson (Lord Kelvin) in 1848 as a way to express temperature in absolute terms. He recognized that any negative temperature in Celsius was just an arbitrary distance below zero; what mattered scientifically was the distance from absolute zero. Kelvin is the SI base unit for temperature.
Why scientists prefer Kelvin
Many physical laws have simpler forms in Kelvin. The ideal gas law (PV = nRT) requires T in Kelvin; using Celsius would require an awkward offset. Blackbody radiation laws (Stefan-Boltzmann, Wien's law) also use Kelvin natively. Thermodynamic efficiency formulas use absolute temperature ratios, which only make sense in Kelvin.
Photography and Kelvin
The "color temperature" of a light source is measured in Kelvin. Incandescent bulbs are around 2700-3200 K (warm orange). Halogen is 3200 K. Daylight is 5500-6500 K. Cloudy day is 7000 K. Camera white balance settings use these numbers so the camera can render colors correctly under each light source.
Add 273.15 to Celsius to get Kelvin. So 0°C = 273.15 K, 20°C = 293.15 K, 100°C = 373.15 K. No multiplication needed; just shift by 273.15.
Subtract 273.15 from Kelvin to get Celsius. So 300 K = 26.85°C, 273.15 K = 0°C, 373.15 K = 100°C.
The Kelvin scale uses the same degree size as Celsius but starts at absolute zero (the theoretical lowest possible temperature). Absolute zero is -273.15°C, which by definition equals 0 K. So adding 273.15 shifts a Celsius reading to the Kelvin scale.
0 Kelvin (-273.15°C) is the theoretical temperature at which all molecular motion stops. It cannot be reached in practice (the laws of thermodynamics prevent it), but laboratories have come within billionths of a degree. Most physics formulas use Kelvin because absolute zero is the natural reference point.
Scientific work: chemistry (gas laws), physics (thermodynamics, color temperature, blackbody radiation), astronomy (star temperatures). Engineering: HVAC systems, semiconductor work, cryogenics. Photography and video: white balance is measured in Kelvin (3200 K tungsten, 5500 K daylight, 7000 K cloudy).
About 293 K to 295 K (20-22°C, the typical comfortable indoor temperature). Body temperature (37°C) is 310 K. Water boils at 373.15 K.
In laboratory plasma experiments, scientists have created temperatures above 10 trillion Kelvin. In nature, the core of the Sun reaches 15 million K. The temperature just after the Big Bang is estimated at over 10^32 K. Everyday "high" temperatures (an oven at 250°C = 523 K) seem mild by comparison.
No. By convention, Kelvin is written without a degree symbol: 300 K, not 300°K. This emphasizes that Kelvin is an absolute scale, not a relative one. Celsius and Fahrenheit use the degree symbol because they are relative to specific reference points (freezing and boiling water, or a salt-ice mixture).
Historical convention codified by the International System of Units (SI) in 1967. Lord Kelvin's name is honored without the degree symbol; the unit is simply "the kelvin", abbreviated K.
Exact. The offset of 273.15 is the SI-defined conversion between Celsius and Kelvin. The calculator shows results to 6 significant figures, which exceeds the precision of any real-world temperature measurement.
Yes. All conversions run in your browser. Nothing is uploaded.