How to Convert Celsius to Kelvin (Formula + Examples)
Kelvin is the temperature scale used in science, and converting between Celsius and Kelvin is a common need in physics, chemistry and engineering. The good news: it's the simplest temperature conversion there is. This guide shows how to convert Celsius to Kelvin (and back) with the formula, examples, and a free converter.
🌡️ Try the Unit Converter now — freeOpen →Scientific formulas and data use Kelvin because it starts at absolute zero — the coldest possible temperature — with no negative values. Being able to convert between everyday Celsius and scientific Kelvin is essential for students and anyone working with scientific data.
The simple formula
To convert Celsius to Kelvin, just add 273.15: 25°C + 273.15 = 298.15 K. To go back, subtract 273.15: 300 K − 273.15 = 26.85°C. Unlike Celsius-to-Fahrenheit, there's no multiplication — the two scales use the same size degree, just a different starting point.
That's the whole conversion. A degree change in Celsius equals a degree change in Kelvin; only the zero point differs.
What Kelvin is and key points
- 0 K is absolute zero — the coldest possible temperature.
- 0°C (water freezes) = 273.15 K.
- 100°C (water boils) = 373.15 K.
- Kelvin has no degree symbol and no negative values in normal use.
- The Kelvin and Celsius degree are the same size.
Step-by-step
Common mistakes to avoid
Pro tips
Frequently asked questions
How do I convert Celsius to Kelvin?
Add 273.15. For example, 25°C + 273.15 = 298.15 K.
How do I convert Kelvin to Celsius?
Subtract 273.15. So 300 K − 273.15 = 26.85°C.
What is 0°C in Kelvin?
273.15 K — the temperature at which water freezes.
Why is Kelvin used in science?
It starts at absolute zero with no negative values, which makes scientific formulas and calculations cleaner.
Is the converter free?
Yes — free with no sign-up, giving exact conversions instantly.
Celsius to Kelvin is the easiest temperature conversion: just add 273.15 (and subtract to reverse). The degree size is the same — only the zero point differs. Remember 0°C = 273.15 K, and use the free converter for exact scientific figures.