Quick Answer: Celsius to Kelvin
0 °C equals 273.15 K, and 1 °C equals 274.15 K (K = °C + 273.15).
Conversely, 1 K = -272.15 °C.
Formula: K = °C + 273.15
Worked examples
- -273.15 °C = 0 K
- -100 °C = 173.15 K
- -40 °C = 233.15 K
Method and limitations
To convert Celsius to Kelvin, add 273.15 to the Celsius value. Kelvin uses the same scale as Celsius but starts at absolute zero. Calculations use full-precision constants; displayed values are rounded to at most 9 significant figures. Temperature scales use an offset, not a single multiplier, so you cannot scale results proportionally: doubling the input does not double the output.
Each factor is exact by definition, derived from exact definitions, or a documented conventional value — see the methodology and sources.
Conversion Formula
To convert Celsius to Kelvin, add 273.15 to the Celsius value. Kelvin uses the same scale as Celsius but starts at absolute zero.
Step-by-Step Conversion Guide
Follow these steps to convert celsius to kelvin manually:
Start with your value in celsius
Example: You want to convert -40 °C
Apply the conversion formula
Use the formula: K = °C + 273.15
Calculate the result
-40 °C = 233.15 K
Verify your answer
Use our calculator above to double-check your manual calculation.
Quick Mental Math Tip
To convert Celsius to Kelvin, add 273.15 to the Celsius value. Kelvin uses the same scale as Celsius but starts at absolute zero.
Common Conversions
| Celsius (°C) | Kelvin (K) | Kelvin → Celsius |
|---|---|---|
| -273.15 °C | 0 | -273.15 K = -546.3 °C |
| -100 °C | 173.15 | -100 K = -373.15 °C |
| -40 °C | 233.15 | -40 K = -313.15 °C |
| 0 °C | 273.15 | 0 K = -273.15 °C |
| 20 °C | 293.15 | 20 K = -253.15 °C |
| 25 °C | 298.15 | 25 K = -248.15 °C |
| 37 °C | 310.15 | 37 K = -236.15 °C |
| 100 °C | 373.15 | 100 K = -173.15 °C |
| 500 °C | 773.15 | 500 K = 226.85 °C |
| 1000 °C | 1,273.15 | 1000 K = 726.85 °C |
Did You Know?
Temperature conversion is the only unit conversion that isn't a simple multiplication — it involves both scaling and offsetting.
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Conversion factors on this page are either exact by definition, derived from exact definitions, or conventional values in documented use. Each is listed with its source in our conversion methodology and sources, which cites the BIPM SI Brochure, NIST Special Publication 811 and the relevant IEC or national standards. Results are rounded for display only; calculations use full precision.