Converting Celsius to Kelvin is a common temperature conversion used in science, education, engineering, and many technical fields. Both Celsius and Kelvin are metric temperature scales, which makes the conversion particularly simple. Unlike Celsius, however, Kelvin is an absolute temperature scale that starts at absolute zero.
In this guide, we will explain what Celsius and Kelvin mean, provide the correct conversion formula, and walk through several practical examples.
What Is Celsius?
Celsius (°C) is one of the most widely used temperature scales in the world. It is commonly used for weather forecasts, cooking, household temperatures, and everyday measurements.
On the Celsius scale, water freezes at 0°C and boils at 100°C under standard atmospheric pressure. The scale is divided into 100 equal degrees between these two reference points.
What Is Kelvin?
Kelvin (K) is the SI base unit of thermodynamic temperature. It is widely used in physics, chemistry, engineering, astronomy, and other scientific fields.
Unlike Celsius, Kelvin does not use the degree symbol. Temperatures are written simply as K, such as 273.15 K.
The Kelvin scale begins at absolute zero, the lowest theoretically possible temperature. Absolute zero is equal to 0 K, which corresponds to approximately −273.15°C.
Celsius to Kelvin Formula
The formula for converting Celsius to Kelvin is very simple:
K = °C + 273.15
To convert a Celsius temperature into Kelvin, simply add 273.15 to the Celsius value.
For example:
20°C + 273.15 = 293.15 K
Therefore, 20°C equals 293.15 K.
Celsius to Kelvin Examples
Convert 0°C to Kelvin
Using the formula:
0 + 273.15 = 273.15 K
Therefore:
0°C = 273.15 K
This is the freezing point of water under standard atmospheric pressure.
Convert 10°C to Kelvin
10 + 273.15 = 283.15 K
Therefore:
10°C = 283.15 K
Convert 20°C to Kelvin
20 + 273.15 = 293.15 K
Therefore:
20°C = 293.15 K
Convert 25°C to Kelvin
25 + 273.15 = 298.15 K
Therefore:
25°C = 298.15 K
Convert 100°C to Kelvin
100 + 273.15 = 373.15 K
Therefore:
100°C = 373.15 K
This corresponds to the boiling point of water under standard atmospheric pressure.
Convert −40°C to Kelvin
−40 + 273.15 = 233.15 K
Therefore:
−40°C = 233.15 K
Celsius to Kelvin Conversion Table
| Celsius | Kelvin |
|---|---|
| −100°C | 173.15 K |
| −50°C | 223.15 K |
| −40°C | 233.15 K |
| −20°C | 253.15 K |
| 0°C | 273.15 K |
| 10°C | 283.15 K |
| 20°C | 293.15 K |
| 25°C | 298.15 K |
| 30°C | 303.15 K |
| 50°C | 323.15 K |
| 75°C | 348.15 K |
| 100°C | 373.15 K |
Why Is Celsius to Kelvin Conversion Important?
Celsius to Kelvin conversion is particularly important in scientific calculations. Many physics and chemistry formulas require temperature to be expressed in Kelvin because Kelvin is an absolute temperature scale.
For example, scientific calculations involving gases, thermodynamics, and energy often use Kelvin rather than Celsius.
Kelvin is also useful because it does not have negative values for ordinary thermodynamic temperatures. The starting point of the scale is absolute zero, represented as 0 K.
Celsius and Kelvin Have the Same Temperature Intervals
One useful feature of these two scales is that a change of 1°C is equal to a change of 1 K.
For example, an increase from 20°C to 30°C is a change of 10°C. On the Kelvin scale, the corresponding change from 293.15 K to 303.15 K is exactly 10 K.
The difference between the scales is their starting point, not the size of their individual units.
Common Conversion Mistake
One common mistake is adding 273 instead of 273.15 when precise scientific calculations are required.
For everyday purposes, K = °C + 273 may provide a reasonable approximation. However, when accuracy matters, use the full formula:
K = °C + 273.15
Also remember that Kelvin temperatures are written without the degree symbol. For example, write 300 K, not 300°K.
Conclusion
Converting Celsius to Kelvin is one of the simplest temperature conversions. The formula is:
K = °C + 273.15
Simply add 273.15 to the Celsius temperature to find the equivalent Kelvin value.
For example, 25°C = 298.15 K, while 100°C = 373.15 K. Understanding this conversion is especially useful in science, engineering, physics, and chemistry, where Kelvin is commonly required for temperature-related calculations.