Convert Kelvin to Celsius (K → °C)

The Kelvin is the SI thermodynamic temperature scale, starting at absolute zero and used in all scientific work.

Kelvin

Celsius

-272.15

1 K-272.15 °CNIST · BIPM accuracy

Kelvin to Celsius Conversion Table

10 common values

Kelvin	Celsius
-40 K	-313.15 °C
-20 K	-293.15 °C
0 K	-273.15 °C
10 K	-263.15 °C
20 K	-253.15 °C
25 K	-248.15 °C
30 K	-243.15 °C
37 K	-236.15 °C
100 K	-173.15 °C
200 K	-73.15 °C

How to Convert Kelvin to Celsius Manually

Step by Step

Temperature scales differ in both zero-point and degree size, so conversion uses a formula — not simple multiplication. Follow these steps to convert kelvins to degrees Celsius by hand.

1
Take your value in kelvins
Start with the number of kelvins (K) you want to convert.
2
Apply the formula
Use the formula: °C = K − 273.15
3
Read the result in degrees Celsius
The result is your value in degrees Celsius (°C).

Practical Examples

1 K

equals

-272.15 °C

5 K

equals

-268.15 °C

10 K

equals

-263.15 °C

25 K

equals

-248.15 °C

100 K

equals

-173.15 °C

Formula

Temperature conversion uses an offset formula, not simple multiplication.

Forward°C = K − 273.15

ReverseK = °C + 273.15

Tips

Use these in everyday conversions

K = °C + 273.15. Identical degree size; only the zero point differs.
There are no "degrees Kelvin" — just "kelvins". The symbol is K, not °K.
Colour temperature: 3000 K warm/yellow; 5000 K daylight; 6500+ K cool/blue.

Common Mistakes

Avoid these

Writing °K — incorrect. Kelvin uses no degree symbol.
Trying to use negative Kelvin values — impossible physically.
Confusing "kelvin" (unit) with "Kelvin" (the scientist William Thomson).

About Kelvin and Celsius

What is the Kelvin?

The Kelvin is the SI base unit of thermodynamic temperature, named after British physicist William Thomson, 1st Baron Kelvin (1824–1907), who proposed an absolute temperature scale in 1848. Kelvin starts at absolute zero — the theoretical lowest temperature where all classical molecular motion stops — at exactly 0 K. The Kelvin uses the same degree size as Celsius: 0°C = 273.15 K, water boils at 373.15 K. Note that Kelvin temperatures are not preceded by a degree sign (300 K, not 300°K). The Kelvin is essential in scientific work — gas laws, blackbody radiation, cryogenics, and astrophysics all use absolute temperature. Since 2019, the Kelvin has been defined by fixing the numerical value of the Boltzmann constant (k = 1.380649 × 10⁻²³ J/K). The Kelvin relates to Celsius by addition (K = °C + 273.15) and is universally used in physics and chemistry.

Scientific and engineering thermodynamics
Astronomy and astrophysics temperature reporting
Colour temperature of light sources (e.g., 6500 K daylight)

Real-world examples

Room temperature ≈ 293 K. Water boils at 373 K. The Sun's surface is 5778 K. Deep space is about 2.7 K.

What is the Celsius?

Celsius is the global temperature scale used for weather forecasts, science, medicine, and daily life in all countries except the United States. Originally proposed by Swedish astronomer Anders Celsius in 1742 (with 0° as boiling and 100° as freezing — the inverse of today's scale), the modern version was reversed shortly after his death. Since 2019, Celsius has been redefined via the Kelvin scale: 0°C is exactly 273.15 K, and 1°C equals 1 K in size. Water freezes at 0°C, boils at 100°C at sea level, and human body temperature is around 37°C. Comfortable room temperature is about 20–22°C, and a hot summer day is 30–35°C. Celsius relates to Fahrenheit by the formula °F = °C × 9/5 + 32, and to Kelvin by adding 273.15. The scale's decimal-friendly division of water's phase transitions made it the natural metric choice.

Daily weather forecasts worldwide (except US)
Cooking temperatures in Europe, Asia, Latin America
Body temperature on medical thermometers

Real-world examples

Room temperature is about 20 °C. Normal body temperature is 37 °C. Typical fridge setting is 4 °C. European winter can reach −20 °C; desert summer 45+ °C.