How do I convert Celsius to kelvin?
Type a value in either box, and the answer shows it in the other unit as you type.
- Kelvins (K)
- 298.15
25 °C = 298.15 K.
Kelvins (K): 298.15. 25 °C = 298.15 K.
Kelvins (K) by degrees Celsius (°C)
How to calculate
Converts degrees Celsius (°C) to kelvins (K) and back, with the exact unit definitions.
Example with the default inputs (Degrees Celsius (°C) 25): 25 °C = 298.15 K.
Formula: K = °C + 273.15
- A kelvin and a degree Celsius are the same size; the scales differ only in their zero: 0 K is −273.15 °C.
- Nothing is colder than absolute zero (0 K, −273.15 °C, −459.67 °F), so a value below it gives no answer.
- Exact on the typed decimals: at most 6 decimal places (6 significant digits below 0.0001), rounded half up; an answer of 1 billion or more shows at most 15 significant digits.
Worked examples
Each example is checked against the calculator on every build.
- Degrees Celsius (°C) 0 gives Kelvins (K) 273.15.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
- Degrees Celsius (°C) 25 gives Kelvins (K) 298.15.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
- Kelvins (K) 298.15 gives Degrees Celsius (°C) 25.Source: Exact unit definitions in NIST SP 811 (2008), Appendix B.8
Other questions people ask
What is the formula to convert Celsius to kelvin?
K = °C + 273.15. For example, 25 °C is 298.15 K.
How do I convert Celsius to kelvin?
Use K = °C + 273.15. 25 °C gives 298.15 K.
How do I convert kelvin back to Celsius?
Reverse the formula, or type the kelvins into the second box and the converter works it out.
What is absolute zero?
0 K, the coldest possible temperature: −273.15 °C, or −459.67 °F. The kelvin scale starts there, so a temperature in kelvin is never negative, and the converter gives no answer below it.
What is 0 °C in kelvin?
273.15 K: add 273.15. 100 °C is 373.15 K, and −40 °C is 233.15 K.
Is it "degrees kelvin"?
No. The unit is the kelvin, written with the symbol K and no degree sign, as in 300 K; NIST SP 811 writes T0 = 273.15 K. Celsius keeps the degree sign: 26.85 °C.