Temperature conversion
Celsius to Kelvin (°C to K)
Express a Celsius reading on the kelvin scale by adding 273.15. The size of each step stays the same; only the zero point changes.
Convert Celsius to Kelvin using K = C + 273.15.
A temperature reading of 0 °C
- Starting measurement
- 0 °C
- Converted value (rounded if needed)
- 273.15 K
Write the result with K, without a degree sign. For a temperature difference rather than a reading, the numerical size is already the same in Celsius degrees and kelvins.
Celsius to Kelvin conversion chart
| Celsius | Kelvin |
|---|---|
| -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 |
| 18 °C | 291.15 K |
| 20 °C | 293.15 K |
| 22 °C | 295.15 K |
| 25 °C | 298.15 K |
| 28 °C | 301.15 K |
| 30 °C | 303.15 K |
| 35 °C | 308.15 K |
| 37 °C | 310.15 K |
| 40 °C | 313.15 K |
| 50 °C | 323.15 K |
| 100 °C | 373.15 K |
| 180 °C | 453.15 K |
How to convert by hand
Formula for a temperature reading
K = C + 273.15
- Start with the reading in Celsius and apply the formula in the order shown.
- Keep the offset exactly as written. It changes the zero point of the scale.
- Round the result to suit your measurement, after completing the calculation.
Related conversions
About Celsius and Kelvin
These pages convert temperature readings. A temperature change is a different calculation: offsets cancel when comparing two readings. Celsius and kelvin have equal-sized steps; Fahrenheit steps are smaller.
Celsius
Metric (SI derived)A Celsius reading is the kelvin reading minus 273.15. Water freezes near 0 °C and boils near 100 °C at standard atmospheric pressure; these are useful reference points rather than the scale’s definition.
Commonly used for: Weather forecasts, oven settings and thermometer readings.
Kelvin
Metric (SI)The SI base unit of thermodynamic temperature, starting at absolute zero. One kelvin is the same size as one degree Celsius. Write K without a degree sign.
Commonly used for: Scientific temperature readings and calculations that use an absolute temperature scale.
Questions
Should I multiply Celsius by a kelvin conversion factor?
No. Add 273.15 to convert a reading. Celsius and kelvin have equal-sized steps, so there is no scale multiplier. A change of one degree Celsius is a change of one kelvin.
How do I convert Kelvin back to Celsius?
Use our Kelvin to Celsius converter, which applies the inverse formula.
Why might the chart and calculator show different decimal places?
The chart uses a compact rounded display. The editable calculator can show up to six decimal places and uses the factors or temperature formulas stored in the library. More displayed digits do not make the original measurement more precise.
Precision and source
The calculator uses stored conversion factors and temperature formulas, then rounds the result for display. A short decimal in a chart is not a claim of exactness. For a calculation with several steps, keep as much precision as the original measurement supports and round at the end.
Reference: NIST SP 811 conversion factors. Its alphabetical tables distinguish unit variants and temperature readings from intervals. Published by ToolsNow. Report a conversion problem.
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