Convert Kelvin to Celsius
Convert kelvins to degrees celsius instantly. °C = K − 273.15 — use the live calculator, the exact formula, a reference-temperature table and worked examples. Also check the Celsius to Kelvin converter for the reverse conversion.
Units explained
Kelvin
The kelvin (K) is the SI base unit of thermodynamic temperature, defined by fixing the Boltzmann constant k at exactly 1.380649×10⁻²³ J/K. Zero kelvin is absolute zero, the lowest temperature physically possible, and kelvin values are written without a degree sign.
Named for William Thomson, 1st Baron Kelvin, who in 1848 calculated the value of absolute zero (about −273 °C) and proposed an absolute thermodynamic scale. His title comes from the River Kelvin, which flows past the University of Glasgow in Scotland.
The universal temperature unit of science and engineering — physics, chemistry, astronomy, and materials science — and the standard for color temperature in photography, displays, and lighting (a 5600 K daylight bulb).
Proposed by William Thomson (Lord Kelvin) in 1848; adopted as an SI base unit by the 10th CGPM in 1954 and redefined through the fixed Boltzmann constant by the 26th CGPM, effective May 20, 2019.
Celsius
The degree Celsius (°C) is the SI's everyday temperature unit. One degree Celsius is exactly the same size as one kelvin, with the zero point shifted so that 0 °C = 273.15 K. Water freezes near 0 °C and boils near 100 °C at standard atmospheric pressure.
Named for Swedish astronomer Anders Celsius, who in 1742 proposed a 100-degree scale between the boiling and freezing points of water. His original scale ran in reverse (0 at boiling, 100 at freezing); it was inverted to the modern direction shortly after his death.
The world's standard everyday temperature scale, used in nearly every country — including throughout India — for weather forecasts, cooking, medicine, science classrooms, and industry.
Devised by Anders Celsius at Uppsala University, Sweden, in 1742; the inverted modern form was in use by 1745, and the name 'degree Celsius' replaced 'degree centigrade' internationally at the 9th CGPM in 1948.
Kelvin to Celsius conversion formula
The exact relationship between kelvins and degrees celsius:
To convert kelvins to degrees celsius, subtract 273.15 from the value. To reverse, add 273.15 to the value.
Reference anchors: water freezes at 273.15 K = 0 °C and boils at 373.15 K = 100 °C (at standard atmospheric pressure).
How to use this converter
Type a value into the calculator. The result in degrees celsius updates as you type. Tap a quick value, copy the result with one click, or use the swap arrow to jump straight to the Celsius to Kelvin converter for the reverse direction.
Step-by-step: convert kelvins to degrees celsius
- Write down the temperature in kelvins (K).
- Subtract 273.15 from the value.
- The result is the same temperature expressed in degrees celsius (°C).
- To reverse, add 273.15 to the value — or open the Celsius to Kelvin converter.
Worked examples
Example 1 — Convert 310.15 K to °C (human body temperature):
310.15 − 273.15 = 37 °C
Example 2 — Convert 373.15 K to °C (the boiling point of water):
373.15 − 273.15 = 100 °C
Kelvin to Celsius conversion table
Physically meaningful reference temperatures, from absolute zero to the surface of the Sun, converted from kelvins to degrees celsius:
| Kelvin [K] | Celsius [°C] | Reference point |
|---|---|---|
| 0 | -273.15 | Absolute zero |
| 233.15 | -40 | Where Celsius and Fahrenheit coincide (−40°) |
| 255.3722222222 | -17.7777777778 | Zero Fahrenheit (0 °F) |
| 273.15 | 0 | Water freezes (0 °C / 32 °F) |
| 273.16 | 0.01 | Triple point of water |
| 283.15 | 10 | Cool day (10 °C / 50 °F) |
| 293.15 | 20 | Room temperature (20 °C / 68 °F) |
| 298.15 | 25 | Standard laboratory temperature (25 °C) |
| 303.15 | 30 | Hot day (30 °C / 86 °F) |
| 310.15 | 37 | Human body temperature (37 °C / 98.6 °F) |
| 313.15 | 40 | Heat-wave day (40 °C / 104 °F) |
| 323.15 | 50 | Hot tap water (50 °C / 122 °F) |
| 373.15 | 100 | Water boils (100 °C / 212 °F) |
| 453.15 | 180 | Moderate baking oven (180 °C / 356 °F) |
| 5778 | 5504.85 | Surface of the Sun (≈5,505 °C) |
Frequently asked questions
What is 310.15 K in °C?
How do I convert kelvins to degrees celsius?
How do I convert degrees celsius back to kelvins?
Do the Kelvin and Celsius scales ever read the same number?
Can a temperature be below absolute zero?
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Sources & references
Conversion relationship (°C = K − 273.15) verified against the following authoritative sources:
- BIPM — The International System of Units (SI Brochure 9th ed.)
Official BIPM publication defining the seven SI base units (including the meter) and the rules for their use. The global authority on units of measurement.
- NIST — Guide to the SI
US National Institute of Standards and Technology reference covering the SI base and derived units with definitions and usage rules for US technical practice.
- NIST Special Publication 811 — Guide for the Use of the International System of Units
Detailed NIST guide covering exact conversion factors between SI and US customary units along with formatting and rounding conventions.
- BIPM — International Temperature Scale of 1990 (ITS-90)
The internationally agreed practical temperature scale, defining fixed points (including the triple point of water at 273.16 K) and interpolation instruments used by national metrology institutes for thermometer calibration worldwide.
- CODATA Internationally Recommended Values of the Fundamental Physical Constants
Committee on Data of the International Science Council; authoritative source for the masses of fundamental particles (electron, proton, neutron) and the atomic mass constant.