Kelvin to Celsius Converter (K to °C)
Convert Kelvin to Celsius and Celsius to Kelvin instantly, with adjustable precision and a step-by-step derivation for every result.
Kelvin cannot go below 0 K (absolute zero). Celsius cannot go below −273.15 °C.
The formulas
Kelvin to Celsius: subtract 273.15.
Example: 300 K − 273.15 = 26.85 °C.
Celsius to Kelvin: add 273.15.
Example: 20 °C + 273.15 = 293.15 K.
The two scales use exactly the same size degree; only their zero points differ. The offset 273.15 is exact: 0 °C is defined as 273.15 K.
About this Kelvin to Celsius calculator
This Kelvin to Celsius calculator is also a full Celsius to Kelvin calculator and Celsius to Kelvin converter: it handles the Kelvin to Celsius conversion and the reverse Celsius to Kelvin conversion (K to Celsius and Celsius to K, or in shorthand K to C and C to K) in one live tool. Wondering how to convert Kelvin to Celsius? Subtract 273.15. How to convert Celsius to Kelvin? Add 273.15. That is the whole Kelvin to Celsius formula (°C = K − 273.15) and the Celsius to Kelvin formula (K = °C + 273.15); the Kelvin Celsius offset of 273.15 is exact, which is why 273.15 appears everywhere on this page and why 273.15 — not 273 — is the right number to use. To convert Kelvin to Celsius in head, just subtract 273 for a quick estimate (300 K in Celsius is about 27 °C; exactly 300 K in Celsius is 26.85 °C). Common checks: is 0 Celsius 273.15 Kelvin? Yes. Kelvin vs Celsius: the degree size is identical, only the zero differs. Absolute zero Kelvin Celsius anchor: 0 K = −273.15 °C; the freezing point of water in Kelvin is 273.15 K. A note on notation (Kelvin symbol no degree): write 300 K, never 300 °K — so if you ask “do you write degree Kelvin?”, the answer is no. The landmark temperatures Kelvin table above covers absolute zero, cryogenics, room and body temperature, and the Sun.
Landmark temperatures
Quick conversion table
| Kelvin (K) | Celsius (°C) | Landmark |
|---|---|---|
| 0 | −273.15 | Absolute zero |
| 2.725 | −270.425 | Cosmic microwave background |
| 4.2 | −268.95 | Liquid helium boils |
| 77 | −196.15 | Liquid nitrogen boils |
| 233.15 | −40 | −40 °C equals −40 °F crossover |
| 273.15 | 0 | Water freezes |
| 273.16 | 0.01 | Triple point of water |
| 293.15 | 20 | Room temperature |
| 294.15 | 21 | Room temperature (warm) |
| 300 | 26.85 | Warm day |
| 310.15 | 37 | Human body temperature |
| 373.15 | 100 | Water boils |
| 5778 | 5504.85 | Sun's surface |
Frequently asked questions
What is the formula to convert Kelvin to Celsius?
Subtract 273.15 from the Kelvin temperature: °C = K − 273.15. For example, 300 K − 273.15 = 26.85 °C.
How do I convert 300 Kelvin to Celsius?
Use the formula °C = K − 273.15. So 300 − 273.15 = 26.85, which means 300 K equals 26.85 °C.
What is 0 Kelvin in Celsius?
0 K equals −273.15 °C. This is absolute zero, the lowest temperature physically possible, so no negative Kelvin values exist.
Is 0 °C the same as 273.15 K?
Yes. Add 273.15 to the Celsius value: 0 + 273.15 = 273.15, so 0 °C equals exactly 273.15 K.
How do I convert Celsius to Kelvin?
Add 273.15 to the Celsius temperature: K = °C + 273.15. For example, 20 °C + 273.15 = 293.15 K.
Why is the conversion number 273.15 and not just 273?
Because 273.15 is the exact measured offset between the two scales: absolute zero sits at −273.15 °C, which is defined as 0 K. Rounding it to 273 would introduce error, for example 20 °C would become 293 K instead of the exact 293.15 K.
Can Kelvin be negative?
No. The Kelvin scale starts at 0 K, absolute zero, and has no negative values. The coldest possible Celsius reading is −273.15 °C, which equals 0 K.
What is the difference between Kelvin and Celsius?
A kelvin and a degree Celsius are exactly the same size; only their zero points differ. The Kelvin scale starts at absolute zero, while the Celsius scale starts at the freezing point of water, so K = °C + 273.15.
Why do scientists use Kelvin instead of Celsius?
Kelvin has no negative values and starts at absolute zero, so a temperature in kelvin is directly proportional to thermal energy. That makes ratios meaningful, which the gas laws and thermodynamics require: doubling from 100 K to 200 K doubles the average kinetic energy, but doubling from 100 °C to 200 °C does not.
What is normal body temperature in Kelvin?
Average human body temperature is 37 °C, and 37 + 273.15 = 310.15, so it equals 310.15 K.
What is room temperature in Kelvin?
Room temperature of 20 °C equals 293.15 K (20 + 273.15). A slightly warmer room at 21 °C equals 294.15 K.
Do you write Kelvin with a degree symbol?
No. The correct symbol is a plain capital K with no degree sign: write 300 K, not 300 °K. Celsius keeps its degree sign as °C.
What is the boiling point of water in Kelvin?
Water boils at 100 °C at standard atmospheric pressure, and 100 + 273.15 = 373.15, so the boiling point is 373.15 K.
How can I convert Kelvin to Celsius in my head?
Subtract 273 from the Kelvin value for a quick estimate, or 273.15 for the exact answer. For example, 300 K is about 27 °C, and exactly 26.85 °C.
Related converters: Kelvin to Fahrenheit · Celsius to Fahrenheit · Temperature converter (all 5 scales)
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