Celsius to Kelvin Conversion Formula — How to Convert °C to K
K = °C + 273.15
For rough work, many textbooks add 273 instead. Use 273.15 when a question asks for precision.
Step-by-Step °C to K Conversion Examples:
- •Room temperature, 20°C:20 + 273.15 =293.15 K
- •Normal body temperature, 37°C:37 + 273.15 =310.15 K
- •Boiling water, 100°C:100 + 273.15 =373.15 K
- •Dry ice sublimation, −78.5°C:−78.5 + 273.15 =194.65 K
Why the Celsius to Kelvin Conversion Works & Common °C to K Converter Mistakes to Avoid
The kelvin is the SI unit of temperature and it starts at absolute zero, the lowest possible temperature, which is −273.15°C. A kelvin is the same size as a Celsius degree, so converting only moves the zero point by 273.15. Since 2019 the kelvin has been defined from a fixed value of the Boltzmann constant rather than from the properties of water.
The Common °C to K Converter Mistake: Writing "degrees Kelvin" or "°K". The correct form is kelvin with a capital K and no degree sign: 298.15 K, not 298.15°K. Another frequent error is adding 273.15 to a Fahrenheit value, which gives a meaningless number. Convert Fahrenheit to Celsius first. Finally, make sure the result is never negative. A kelvin value below 0 K is impossible.
Celsius to Kelvin Real-World Size Comparison Table
These are the temperatures that appear most often in school and lab work, from absolute zero to the boiling point of water.
| Celsius (°C) | Kelvin (K) | Real-World Size Benchmark |
|---|---|---|
| -273.15 °C | 0 K | Absolute zero, the lowest possible temperature |
| -196 °C | 77.15 K | Liquid nitrogen boils at about this temperature |
| -78.5 °C | 194.65 K | Dry ice turns directly to gas |
| -40 °C | 233.15 K | The point where Celsius and Fahrenheit match |
| 0 °C | 273.15 K | Water freezes at standard pressure |
| 15 °C | 288.15 K | The standard sea-level atmosphere temperature |
| 20 °C | 293.15 K | A typical room temperature |
| 25 °C | 298.15 K | Standard ambient temperature used in chemistry |
| 37 °C | 310.15 K | Average human body temperature |
| 100 °C | 373.15 K | Water boils at sea level |
Where Celsius-to-Kelvin matters
Kelvin is the standard unit in physics, chemistry and engineering. Everyday thermometers use Celsius, so the conversion bridges the two. It is essential whenever a formula, such as a gas law or a radiation equation, needs absolute temperature.
- • Use °C For: Weather and household thermometers, Laboratory readings in Celsius, Cooking and food science data, Everyday temperature measurements
- • Use K For: Gas law calculations (PV = nRT), Thermodynamics problems, Physics and chemistry exams, Scientific papers and datasheets
Rule of Thumb: A change of 1°C is the same size as a change of 1 K. Only the zero point is different.
°C to K Converter in Spreadsheets — Spreadsheet Shortcut (Excel & Google Sheets)
With Celsius in cell A1, =A1+273.15 returns kelvins. For the reverse, use =A1-273.15. The built-in =CONVERT(A1,"C","K") also works and keeps the unit pair visible in the formula.
Celsius to Kelvin Conversion — Frequently Asked Questions
How do I convert Celsius to Kelvin?
Add 273.15 to the Celsius temperature. For example, 25°C + 273.15 = 298.15 K.
What is 0°C in Kelvin?
0°C is 273.15 K, the freezing point of water at standard pressure.
What is 100°C in Kelvin?
100°C is 373.15 K, the boiling point of water at sea level.
What is absolute zero in Celsius?
Absolute zero is −273.15°C, which is 0 K.
What is 25°C in Kelvin?
25°C is 298.15 K, the standard ambient temperature used in many chemistry tables.
Is it Kelvin or degrees Kelvin?
Just kelvin. Since 1967 the unit has been written as K with no degree sign, so 300 K and not 300°K.
Can I use 273 instead of 273.15?
For rough work, yes. For exam answers or lab reports that need precision, use 273.15.
Does a Celsius degree equal a kelvin?
As a size, yes. A temperature change of 1°C equals a change of 1 K. They differ only in where zero sits.
°C to K Quick-Reference Conversion Table
The temperature conversions that come up alongside Celsius to Kelvin.
| To convert | Operation | Example |
|---|---|---|
| °C → K | + 273.15 | 25°C → 298.15 K |
| K → °C | − 273.15 | 300 K → 26.85°C |
| °C → °F | (× 9/5) + 32 | 100°C → 212°F |
| °F → °C | (− 32) × 5/9 | 68°F → 20°C |