Unit converter
Celsius to Kelvin Converter
Convert a Celsius temperature into kelvin, the base unit of the SI system. Scientists, students and engineers work in kelvin because it starts at absolute zero, the coldest anything can get, which makes gas-law and thermodynamic sums far cleaner. Lighting catalogues also quote colour temperature in kelvin, so a warm bulb might read 2700 K. Enter a value in degrees Celsius and the tool returns kelvin, with a reference table of common points. It suits physics or chemistry homework, lab work, and translating a Celsius lab reading into the unit a formula expects.
Common Celsius to Kelvin values
| Celsius | Kelvin |
|---|---|
| 0 °C | 273.15 K |
| 10 °C | 283.15 K |
| 20 °C | 293.15 K |
| 37 °C | 310.15 K |
| 50 °C | 323.15 K |
| 100 °C | 373.15 K |
| 200 °C | 473.15 K |
How to convert
- Take the temperature in degrees Celsius.
- Add 273.15 to it; that figure is where the Celsius scale sits above absolute zero.
- The sum is the temperature in kelvin.
- There is no stretching involved because a kelvin and a Celsius degree are exactly the same size; only the starting point shifts.
- To reverse the step, subtract 273.15 from a kelvin value to return to degrees Celsius.
K = °C + 273.15
Celsius and kelvin run in lockstep: a one-degree change reads the same on both. What differs is the origin. Celsius puts its zero at the freezing point of water, whereas kelvin puts its zero at absolute zero, 273.15 degrees lower. Adding 273.15 slides the Celsius reading onto the absolute scale, with no scaling factor needed.
- °C
- the temperature in degrees Celsius you start with
- 273.15
- the offset between the Celsius zero and absolute zero
- K
- the resulting temperature in kelvin
Worked example
A room at 25°C is 25 plus 273.15, which is 298.15 K. Boiling water at 100°C becomes 100 plus 273.15, giving 373.15 K, while a freezing 0°C lands exactly at 273.15 K.
Key facts
- Absolute zero is 0 K, equal to -273.15°C, the lowest temperature there is.
- Water freezes at 273.15 K and boils at 373.15 K.
- Comfortable room temperature near 20°C is about 293.15 K.
- A kelvin and a Celsius degree represent exactly the same temperature interval.
Tips
- For a quick mental figure, add 273 and ignore the .15; the small error rarely matters outside precise lab work.
- When a physics formula asks for absolute temperature, convert your Celsius readings to kelvin before substituting them in.
Frequently asked questions
What is 0°C in kelvin?+
0°C equals 273.15 K, the point at which water freezes expressed on the absolute scale.
Why does kelvin start at 273.15 below zero Celsius?+
Kelvin is anchored to absolute zero, the lowest possible temperature, and that point falls 273.15 Celsius degrees beneath the freezing point of water.
Do I write a degree symbol with kelvin?+
No. Kelvin takes neither the degree sign nor the word degrees: you write 300 K and say three hundred kelvin.
Is the conversion a simple addition?+
Yes, because the two scales share an identical degree size. Only the offset of 273.15 separates them, so you just add it.
Things to watch
- Write kelvin without a degree symbol; "°K" is incorrect notation and marks down lab reports.
- Negative kelvin values are unphysical, so a result below zero means an arithmetic slip somewhere.
Sources
Last updated: 2026-01-01
Conversions use internationally defined factors. Provided for general use; verify critical measurements independently.