Convert Celsius to Kelvin
Kelvin = Celsius + 273.15. Type any temperature below to convert celsius to kelvin both ways — it runs entirely in your browser.
Celsius to Kelvin formula
Temperature scales have different zero points, so the conversion is a multiply-and-add, not a single ratio:
Kelvin = Celsius + 273.15
To go the other way, Celsius = Kelvin − 273.15.
Worked example
Convert 25 °C to kelvin:
= 25 + 273.15 = 298.15 K.
Common temperatures in Celsius and Kelvin
| Reference point | Celsius (°C) | Kelvin (K) |
|---|---|---|
| Absolute zero | -273.15 | 0 |
| Freezing point of water | 0 | 273.15 |
| Refrigerator | 4 | 277.15 |
| Room temperature | 21 | 294.15 |
| Normal human body temperature | 37 | 310.15 |
| A hot summer day | 45 | 318.15 |
| Boiling point of water (sea level) | 100 | 373.15 |
About the Celsius and Kelvin scales
Celsius: Celsius (centigrade) puts 0° at the freezing point of water and 100° at its boiling point at sea level. It is the everyday temperature scale used almost everywhere outside the United States.
Kelvin: The kelvin is the SI base unit of temperature. It starts at absolute zero (0 K = −273.15 °C) and uses the same degree size as Celsius, so it is written without a degree sign.
Frequently asked questions
- What is 25 °C in Kelvin?
- 25 °C = 298.15 K.
- How do I convert Celsius to Kelvin?
- Use kelvin = celsius + 273.15. For example, 25 °C → 298.15 K.
- How do I convert Kelvin back to Celsius?
- Reverse it: celsius = kelvin − 273.15.
- Why isn't converting Celsius to Kelvin just multiplication?
- Because the two scales start their zero at different temperatures, so after scaling by 1 you also add 273.15. Skipping that constant is the most common temperature-conversion mistake.