Celsius to Kelvin Converter
Celsius (°C) → Kelvin (K)
Also: 77 °F Fahrenheit · 536.67 °R Rankine
Show Your Work
- 1. K = 25 + 273.15
- 2. K = 298.15 K
About this conversion
Kelvin is the SI base unit of thermodynamic temperature and the scale used in almost all chemistry, physics, and thermodynamics work. Celsius and Kelvin share the same degree size, so converting between them is a simple offset of 273.15. This page focuses on the C → K direction for laboratory, classroom, and engineering use cases where you start with a Celsius reading and need the absolute value for an equation like the ideal gas law (PV = nRT).
Celsius to Kelvin Reference Table
| Celsius (°C) | Kelvin (K) |
|---|---|
| -273.15 | 0 |
| -250 | 23.15 |
| -200 | 73.15 |
| -150 | 123.15 |
| -100 | 173.15 |
| -50 | 223.15 |
| -20 | 253.15 |
| 0 | 273.15 |
| 10 | 283.15 |
| 15 | 288.15 |
| 20 | 293.15 |
| 25 | 298.15 |
| 30 | 303.15 |
| 37 | 310.15 |
| 50 | 323.15 |
| 75 | 348.15 |
| 100 | 373.15 |
| 150 | 423.15 |
| 200 | 473.15 |
| 250 | 523.15 |
| 300 | 573.15 |
| 400 | 673.15 |
| 500 | 773.15 |
| 750 | 1023.15 |
| 1000 | 1273.15 |
When to use Celsius → Kelvin
- Plugging a temperature into the ideal gas law or any thermodynamic equation that requires absolute temperature
- Calculating reaction rates with the Arrhenius equation
- Converting between Celsius lab notebook readings and Kelvin values for reports
- Converting cryogenic temperatures recorded in Celsius to Kelvin for low-temperature physics
Worked Example
A reaction is run at 25°C. Convert that to Kelvin for use in the Arrhenius equation.
- Start with the Celsius value: C = 25.
- Add 273.15: 25 + 273.15 = 298.15.
- So 25°C = 298.15 K.
298.15 K is the IUPAC standard ambient temperature (SATP). Many tables of thermodynamic constants are tabulated at this value.
Frequently Asked Questions
What is the formula to convert Celsius to Kelvin?
K = C + 273.15. Add 273.15 to the Celsius value.
What is 0°C in Kelvin?
0°C = 273.15 K. This is the freezing point of water on both scales.
What is 25°C in Kelvin?
25°C = 298.15 K. This is the IUPAC standard ambient temperature, commonly used as the reference for thermodynamic data.
Why is the offset 273.15 and not 273?
The 1954 redefinition of the Kelvin tied it to the triple point of water (273.16 K, 0.01°C). The freezing point under standard pressure is 0.01 K below the triple point, giving 273.15 K. Older textbooks sometimes round to 273, which introduces a 0.15 K error.
Are negative Kelvin values valid?
No. Kelvin starts at absolute zero (0 K = -273.15°C), the theoretical minimum temperature. Any Celsius input below -273.15 produces a negative Kelvin value that doesn't correspond to a real temperature.
More Temperature Conversions
- Kelvin to Celsius — the reverse direction
- Celsius to Fahrenheit — same starting scale, different target
- Celsius to Rankine — same starting scale, different target
- Fahrenheit to Kelvin — different starting scale, same target
- Rankine to Kelvin — different starting scale, same target
- All-scale Temperature Converter — see Celsius, Fahrenheit, Kelvin, and Rankine at once
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