A lab temperature
Room temperature of 25 °C is 298.15 K for a physics calculation.
Use Celsius to Kelvin
Converts celsius to kelvin in this tab, with nothing sent anywhere.
Runs entirely on your deviceThe conversion happens in this browser tab. Nothing you type is uploaded, logged or stored, which is worth knowing for anything you would not paste into a search box.
Room temperature at 20 °C is 293.15 K. Kelvin is an absolute scale, so the conversion adds 273.15 rather than multiplying; a Celsius value below -273.15 would describe a temperature below absolute zero.
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Browse all general convertersAbout Celsius to Kelvin
Kelvin is the temperature scale of science, starting at absolute zero - the coldest anything can be - so it never goes negative. Celsius shares its degree size but starts at water's freezing point. Converting Celsius to Kelvin is the everyday need of physics and chemistry work: just add 273.15. So 0 °C is 273.15 K, and room temperature of 25 °C is 298.15 K, the kind of figure a gas-law calculation requires. Gas-law problems and thermodynamics homework demand Kelvin, because the equations only hold on an absolute scale where zero really means no thermal energy at all. Semiconductor and cryogenics work quote Kelvin because material behaviour is tied to the absolute scale, where a Celsius room reading has to be shifted up before use. A Celsius temperature difference has the same numerical size in kelvin; the offset applies to temperatures, not intervals.
Using Celsius to Kelvin
- Type a number of degrees. You can paste a value with its unit; the tool reads the number.
- The exact factor is applied and the result is shown as K, updating live as you type.
- Copy the answer, or switch to the reverse converter to go from K back to °C.
Where celsius to kelvin helps
Both directions
Need the opposite? The K-to-°C converter is linked below and uses the exact inverse factor.
Use Kelvin when a formula needs absolute temperature
At 20 C the absolute temperature is 293.15 K; at 40 C it is 313.15 K. Doubling the Celsius number therefore does not double the absolute temperature. This matters when inserting a temperature into an equation involving ratios. A difference of 5 C is still a difference of 5 K, because only the origin changes. Kelvin is written K, without a degree symbol.
Before you use the result
- The result is rounded for readability, so a value converted and then converted back may differ in the last decimal place. The underlying factor is exact.
- Units in your input are ignored - only the number is read - so make sure the figure you type is really in °C.
Questions about Celsius to Kelvin
Why add 273.15?
Because Kelvin and Celsius share the same degree size but Kelvin starts at absolute zero, which sits 273.15 degrees below water's freezing point.
Is my data uploaded?
No. Celsius to Kelvin does the arithmetic in this browser tab; the value is calculated on your device and is not sent to a server.
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