Celsius to Kelvin Converter
Convert Celsius to Kelvin instantly. Enter a temperature in °C to get Kelvin by adding 273.15, with the reverse Kelvin to Celsius direction shown.
Updated 2026-06-14 · Free · No sign-up · Runs privately in your browser
Show the formula & steps
How the Celsius to Kelvin Converter Works
This tool converts degrees Celsius (°C) to Kelvin (K) and back. Kelvin is the SI base unit of temperature, used in science and engineering, while Celsius is the everyday metric scale. The two share the same degree size but start at different points.
The Formula
Kelvin = Celsius + 273.15 Celsius = Kelvin − 273.15
Because a one-degree change is identical on both scales, you only need to add or subtract the offset of 273.15.
Worked Example
Convert 25 °C (a warm room) to Kelvin:
- Kelvin = 25 + 273.15 = 298.15 K
The freezing point of water, 0 °C:
- 0 + 273.15 = 273.15 K
Going the other way, 310 K in Celsius:
- Celsius = 310 − 273.15 = 36.85 °C
Celsius to Kelvin Quick Reference
| Celsius (°C) | Kelvin (K) |
|---|---|
| -273.15 | 0 |
| 0 | 273.15 |
| 25 | 298.15 |
| 37 | 310.15 |
| 100 | 373.15 |
Why Kelvin Starts at Absolute Zero
The Kelvin scale begins at absolute zero, the temperature at which molecular motion stops, equal to -273.15 °C. Because it has no negative values, Kelvin is the natural choice for physics formulas such as the ideal gas law, where temperature must be measured from absolute zero. Celsius is more convenient for daily life, which is why scientists routinely convert between the two.
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. To reverse it, subtract 273.15 from the Kelvin value.
What is 0 degrees Celsius in Kelvin?+
0 °C equals 273.15 K. This is the freezing point of water. The Kelvin scale starts at absolute zero, which is -273.15 °C.
Why do you add exactly 273.15?+
The Kelvin and Celsius scales use the same size degree, but Kelvin starts at absolute zero rather than the freezing point of water. Absolute zero sits 273.15 degrees below 0 °C, so adding 273.15 shifts the scale.
Can Kelvin be negative?+
No. Kelvin is an absolute scale starting at 0 K (absolute zero), the coldest possible temperature. There are no negative Kelvin values, which is why this converter rejects temperatures below -273.15 °C.
What is room temperature in Kelvin?+
Room temperature of about 21 °C equals roughly 294 K. Body temperature of 37 °C is about 310 K. Just add 273.15 to any Celsius reading.