Free Celsius to Kelvin Converter
The Kelvin scale is the SI standard for absolute temperature in science and engineering. Convert any Celsius value to Kelvin instantly—whether you're working in a lab, studying thermodynamics, or analyzing astronomical data.
Pick any units and edit either box — it converts instantly in your browser.
Quick answer
To convert Celsius to Kelvin, simply add 273.15. Kelvin is an absolute temperature scale where 0 K (absolute zero) is the lowest possible temperature—the point where all molecular motion theoretically stops.
Formula & method
K = °C + 273.15
Temperature scales have an offset, so this is not a simple multiplication.
Celsius to Kelvin — common values
| Celsius (°C) | Kelvin (K) |
|---|---|
| -273.15 °C | 0 K |
| -40 °C | 233.15 K |
| 0 °C | 273.15 K |
| 25 °C | 298.15 K |
| 37 °C | 310.15 K |
| 100 °C | 373.15 K |
| 200 °C | 473.15 K |
| 1,000 °C | 1,273.15 K |
Examples
- Input
- 0 °C
- Result
- 273.15 K
- Why
- The standard reference point in both Celsius and the scientific definition of the Kelvin scale.
- Input
- 25 °C
- Result
- 298.15 K
- Why
- Standard laboratory conditions; used as a reference in chemistry and materials testing.
- Input
- 37 °C
- Result
- 310.15 K
- Why
- The typical temperature at which human enzymes and metabolic processes function optimally.
- Input
- 100 °C
- Result
- 373.15 K
- Why
- Water transitions from liquid to gas at this temperature at sea level.
Common mistakes
- Treating temperature like a simple multiplication. Because the scales have an offset, you must add or subtract the constant — 0 °C is 32 °F, not 0 °F.
- Converting in the wrong direction. This page goes Celsius → Kelvin; rearrange the formula to reverse it.
Frequently asked questions
Why is Kelvin used in science instead of Celsius?
Kelvin is an absolute temperature scale with no negative values below zero. This makes it ideal for physics and chemistry equations, gas laws (like the ideal gas law), and any calculation involving ratios of temperatures.
What is absolute zero and why does it matter?
Absolute zero (0 K or −273.15°C) is the theoretical lowest possible temperature—the point where all molecular and atomic motion ceases. It is unattainable in practice but forms the foundation of the Kelvin scale and the laws of thermodynamics.
Is the Kelvin scale ever used outside of science?
In everyday life, no. Kelvin is used exclusively in scientific, medical, and industrial contexts—physics, chemistry, astronomy, materials science, and engineering. Celsius and Fahrenheit dominate daily weather and cooking.
What is the difference between Kelvin and Celsius degree size?
There is no difference in degree size. A change of 1°C equals a change of 1 K. The only difference is the offset: Kelvin starts at absolute zero, while Celsius is offset by 273.15 K.
Why is the offset exactly 273.15 and not a round number?
The offset 273.15 is defined by the historical freezing point of water at 0°C combined with the modern definition of Kelvin based on the Boltzmann constant and fixed at the triple point of water (273.16 K, or 0.01°C).
Can Kelvin be negative?
No. Kelvin is an absolute scale—it cannot go below 0 K, which is absolute zero. This is a fundamental property of the scale, unlike Celsius and Fahrenheit, which have negative values.
Sources & references
- BIPM: The Kelvin Scale and Absolute Temperature
- NIST Handbook 44: Specifications, Tolerances, and Other Technical Requirements for Weighing and Measuring Devices
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