The Kelvin and Celsius scales use equal-sized intervals but different zero points. To convert Kelvin to Celsius, subtract 273.15. To convert Celsius to Kelvin, add 273.15.
Kelvin to Celsius Formula
Kelvin to Celsius:
°C = K − 273.15
Celsius to Kelvin:
K = °C + 273.15
The numerical offset is 273.15 because 0 K corresponds to −273.15°C. A temperature interval of 1 K is the same size as an interval of 1°C, but the two scales begin at different zero points.
How to Convert Kelvin to Celsius
- Write down the temperature in Kelvin.
- Subtract 273.15.
- Write the result in degrees Celsius, using the symbol °C.
Example: Convert 300 K to Celsius
Formula: °C = K − 273.15
Substitute: °C = 300 − 273.15
Result: 300 K = 26.85°C
Celsius to Kelvin Formula
To reverse the conversion, add 273.15 to the Celsius temperature:
Example: Convert 25°C to Kelvin
Formula: K = °C + 273.15
Substitute: K = 25 + 273.15
Result: 25°C = 298.15 K
Kelvin to Celsius Conversion Table
| Kelvin (K) | Celsius (°C) | Common Reference |
|---|---|---|
| 0 K | −273.15°C | Absolute zero |
| 77 K | −196.15°C | Approximate liquid nitrogen temperature |
| 100 K | −173.15°C | Low-temperature reference |
| 273.15 K | 0°C | Water freezing reference at standard pressure |
| 293.15 K | 20°C | Typical room temperature |
| 298.15 K | 25°C | Common laboratory reference |
| 300 K | 26.85°C | Common conversion example |
| 310.15 K | 37°C | Approximate human body temperature |
| 373.15 K | 100°C | Water boiling reference at standard pressure |
| 500 K | 226.85°C | High-temperature reference |
Kelvin vs Celsius
| Feature | Kelvin | Celsius |
|---|---|---|
| Symbol | K | °C |
| Scale type | Absolute thermodynamic scale | Offset temperature scale |
| Zero point | Absolute zero | 273.15 K above absolute zero |
| Degree symbol | Not used | Used |
| Interval size | 1 K | 1°C has the same interval size |
| Common use | Science and thermodynamics | Weather, daily use and laboratory reporting |
Absolute Zero and Valid Inputs
For ordinary temperature conversion, Kelvin values cannot be below 0 K. The equivalent Celsius limit is −273.15°C.
The calculator therefore rejects Kelvin values below 0 and Celsius values below −273.15.
Common Conversion Mistakes
- Adding instead of subtracting: subtract 273.15 when converting Kelvin to Celsius.
- Using a degree symbol with Kelvin: write 300 K, not 300°K.
- Rejecting valid negative Celsius values: Celsius can be negative, provided it is not below −273.15°C.
- Entering negative Kelvin: ordinary Kelvin temperatures cannot be below 0 K.
- Rounding too early: complete the conversion before applying the required display precision.
- Confusing values with intervals: a change of 1 K equals a change of 1°C, but 1 K is not the same absolute temperature as 1°C.
How to Check Your Answer
Reverse the calculation. After converting Kelvin to Celsius, add 273.15 to the Celsius answer. After converting Celsius to Kelvin, subtract 273.15 from the Kelvin answer.
Example: 300 K → 26.85°C, and 26.85 + 273.15 = 300 K.
Frequently Asked Questions
Subtract 273.15 from the Kelvin value. The formula is °C = K − 273.15.
0 K equals −273.15°C. This is absolute zero, the lower limit of the thermodynamic temperature scale.
273.15 K equals 0°C.
300 K equals 26.85°C because 300 − 273.15 = 26.85.
For ordinary thermodynamic temperature conversion, no. A valid Kelvin input must be 0 K or higher.
Kelvin is an SI unit written with the symbol K, without the degree sign. Write 300 K, not 300°K.
Yes. One kelvin and one Celsius degree have the same interval size, but the two scales use different zero points.
No. Altitude may change physical boiling points, but the numerical relationship between Kelvin and Celsius always uses the same 273.15 offset.
Calculation Methodology
This converter uses the exact numerical relationship °C = K − 273.15 and K = °C + 273.15. Inputs below 0 K, or below −273.15°C when converting to Kelvin, are rejected. Display rounding is applied only according to the precision selected by the user.
Formula and terminology are based on the International System of Units and published temperature guidance from authoritative metrology sources.
Last reviewed: July 26, 2026
