Celsius to Kelvin Converter
Convert degrees Celsius to kelvins instantly — with formula, examples and table.
Add 273.15 to a Celsius temperature to get kelvin: 25 °C = 298.15 K, 0 °C = 273.15 K. The kelvin is the SI unit and starts at absolute zero, so it never goes negative — which is why science and gas-law calculations use it.
Where you'll meet this conversion
- Room temperature 20 °C = 293.15 K.
- Water boils at 100 °C = 373.15 K.
- Absolute zero: −273.15 °C = 0 K.
Common mistake
Writing "degrees kelvin" or °K — kelvin has no degree sign. Also, temperature differences are the same in both scales: a rise of 10 °C is a rise of 10 K.
Formula: K = °C + 273.15. For example, 20 °C equals 293.15 K.
How to convert degrees Celsius to kelvins
K = °C + 273.15
Celsius sets 0° at water's freezing point and 100° at its boiling point at sea level. It is the world's standard scale for weather and cooking outside the US.
The kelvin starts at absolute zero (−273.15 °C), the coldest temperature physically possible. It is the SI base unit used throughout science.
Celsius to Kelvin conversion table
| Celsius (°C) | Kelvin (K) |
|---|---|
| -40 °C | 233.15 K |
| -30 °C | 243.15 K |
| -20 °C | 253.15 K |
| -10 °C | 263.15 K |
| -5 °C | 268.15 K |
| 0 °C | 273.15 K |
| 5 °C | 278.15 K |
| 10 °C | 283.15 K |
| 15 °C | 288.15 K |
| 20 °C | 293.15 K |
| 25 °C | 298.15 K |
| 30 °C | 303.15 K |
| 35 °C | 308.15 K |
| 37 °C | 310.15 K |
| 40 °C | 313.15 K |
| 45 °C | 318.15 K |
Need the opposite direction? Use the Kelvin to Celsius converter, or read our complete guide to temperature conversions for every formula in one place.
Frequently asked questions
What is the formula to convert Celsius to Kelvin?
K = °C + 273.15. For example, 25 °C equals 298.15 K.
What is 100 °C in K?
100 °C equals 373.15 K, using the formula K = °C + 273.15.
Is my data stored when I use this converter?
No. The conversion runs entirely in your browser with JavaScript — nothing you type is sent to a server, logged or stored.