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 | 0 | -273.15 K = -546.3 °C |
| -100 | 173.15 | -100 K = -373.15 °C |
| -40 | 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 | 773.15 | 500 K = 226.85 °C |
| 1000 | 1273.15 | 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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Last verified: April 2026. All conversion factors are based on internationally defined standards.