Kelvin (K) to Celsius (°C) Converter
Convert Kelvin (K) to Celsius (°C) instantly. Enter any value and get the result. Includes a conversion table and the exact formula.
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How to convert Kelvin (K) to Celsius (°C)
Enter your value
Type the number of kelvin (k) you want to convert into the left box. The result in celsius (°c) appears instantly in the right box. You can also type into the right box to convert in the other direction.
Use the swap button
Click the ⇄ Swap button to reverse the conversion — Celsius (°C) to Kelvin (K). Your current value carries across so you don't have to re-enter anything.
About Kelvin (K) and Celsius (°C)
Kelvin and Celsius use identically sized degrees, so a change of 1 K is the same as a change of 1°C -- only the zero point differs. Celsius is set so that water freezes at 0 and boils at 100, while Kelvin is set so that 0 represents absolute zero, the coldest possible temperature. That's why converting between them is a simple addition or subtraction (273.15) rather than the scaling multiplication used for Fahrenheit.
Kelvin in science and everyday technology
Physics and chemistry calculations
Gas laws, thermodynamics equations, and chemical reaction rates are calculated in Kelvin because the mathematics requires an absolute temperature scale with a true zero -- using Celsius or Fahrenheit in these formulas would produce nonsensical results (like dividing by zero or getting negative volumes) whenever the calculation crosses the Celsius zero point.
Color temperature in lighting and photography
Light bulb packaging and camera white-balance settings use Kelvin to describe color, not heat -- warm household lighting sits around 2700-3000 K (a yellowish glow), while daylight-balanced bulbs and overcast skies sit around 5500-6500 K (a cooler, bluer light). This comes from the physics of heating a theoretical "black body" to that temperature and observing the color it glows.
Astronomy and extreme temperatures
Astronomers report star and cosmic temperatures in Kelvin because many are far too hot or cold to sensibly express in Celsius -- the Sun's surface is about 5,778 K, while the cosmic microwave background left over from the Big Bang is just 2.7 K, barely above absolute zero. Superconductor and cryogenics research similarly works in the single digits or low hundreds of Kelvin.
Subtract 273.15 to convert K to °C. Room temperature (20°C) = 293.15 K. Body temperature (37°C) = 310.15 K. Water freezes at 273.15 K, boils at 373.15 K.
Frequently asked questions
How do I convert Kelvin (K) to Celsius (°C)?
To convert Kelvin to Celsius, subtract 273.15 from the Kelvin value. For example, 300 K minus 273.15 = 26.85°C. Use the calculator above for instant results with any value.
How many Celsius (°C) are in 1 Kelvin (K)?
1 Kelvin equals -272.15°C. Because the Kelvin and Celsius scales share the same size of degree but a different zero point, converting a single unit of Kelvin gives a temperature far below the Celsius scale's zero point.
Is the Kelvin (K) to Celsius (°C) converter free?
Yes, the Kelvin (K) to Celsius (°C) converter is completely free with no sign-up required, no downloads, and it works offline once the page has loaded.
Why does the Kelvin scale start at 0 instead of a negative number?
Zero Kelvin is absolute zero -- the theoretical point at which particles have minimal thermal motion. Lord Kelvin proposed the scale in 1848 so temperature would have a true physical zero point, unlike Celsius or Fahrenheit whose zero points are arbitrary.
Why don't Kelvin temperatures use the degree symbol?
Kelvin is written as "300 K", not "300°K", because SI defines the kelvin as an absolute unit of measurement, like meters or seconds, rather than a relative scale like Celsius or Fahrenheit.
Where is the Kelvin scale actually used?
Kelvin is standard in physics, chemistry, and engineering -- for the temperature of stars, the cosmic microwave background (2.7 K), superconductor research, and color temperature ratings for lighting and cameras (2700-6500 K).
What is the Kelvin equivalent of common temperatures?
Absolute zero is 0 K (-273.15°C). Water freezes at 273.15 K (0°C) and boils at 373.15 K (100°C). Room temperature is roughly 293.15 K, and body temperature is about 310.15 K.