Celsius to Kelvin Converter

Convert Celsius to Kelvin instantly. Accurate absolute temperature conversion for scientific, engineering, and thermodynamic applications.

Absolute Zero
0 K / -273.15°C
Water Freezes
273.15 K / 0°C
Room Temperature
293.15 K / 20°C
Water Boils
373.15 K / 100°C
°C
Enter temperature in degrees Celsius
K
Enter temperature in Kelvin (absolute temperature)
0 K
Absolute Zero 273.15 K
Water Freezes 293.15 K
Room Temp 373.15 K
Water Boils 500 K
High Temp
Absolute Zero
Liquid Nitrogen
Dry Ice (CO₂)
Water Freezes
Room Temperature
Human Body
Water Boils
Paper Burns
Sun Surface
Sun Core
Conversion Result
20°C = 293.15 K
Celsius
20 °C
Degrees Celsius °C
Kelvin
293.15 K
Kelvin K
Fahrenheit
68 °F
Degrees Fahrenheit °F
Rankine
527.67 °R
Degrees Rankine °R
Absolute Temperature Comparison
20°C
Celsius
293.15K
Kelvin
68°F
Fahrenheit
527.67°R
Rankine
Absolute Zero (0 K / -273.15°C)

Theoretical lower limit of temperature where particles have minimal thermal motion.

According to the third law of thermodynamics, absolute zero cannot be reached in a finite number of steps.
Absolute Temperature Scale

Conversion Formulas:

K = °C + 273.15

°C = K - 273.15

Calculation: 20°C + 273.15 = 293.15 K

Note: Kelvin is an absolute temperature scale with its zero point at absolute zero.

Understanding Kelvin and Celsius Temperature Scales

The Celsius (°C) scale is a relative temperature scale based on the properties of water. The Kelvin (K) scale is an absolute temperature scale used in scientific contexts where absolute temperatures are required, such as in thermodynamics and physics.

Kelvin Scale Characteristics:

  • Named after William Thomson, 1st Baron Kelvin (1824-1907)
  • An absolute temperature scale with zero at absolute zero
  • Unit size is the same as the Celsius degree (1 K = 1°C)
  • No negative temperatures (theoretically impossible)
  • SI base unit for thermodynamic temperature

Celsius Scale Characteristics:

  • Named after Anders Celsius (1701-1744)
  • Originally called "centigrade" (100 steps between freezing and boiling)
  • 0°C = freezing point of water at standard atmospheric pressure
  • 100°C = boiling point of water at standard atmospheric pressure
  • Used worldwide for most everyday temperature measurements

Thermodynamic Constants and Reference Points

Temperature Celsius (°C) Kelvin (K) Scientific Significance
Absolute Zero -273.15°C 0 K Theoretical minimum temperature
Triple Point of Water 0.01°C 273.16 K Defining point for Kelvin scale (since 2019)
Water Freezing Point 0°C 273.15 K Ice-water equilibrium at 1 atm
Standard Room Temperature 20°C 293.15 K Common reference for scientific measurements
Human Body Temperature 37°C 310.15 K Average internal temperature
Water Boiling Point 100°C 373.15 K Liquid-vapor equilibrium at 1 atm
Paper Ignition Point 232.8°C 505.95 K Autoignition temperature of paper
Sun Surface Temperature 5,505°C 5,778 K Photosphere temperature
Sun Core Temperature 15,000,000°C 15,000,000 K Nuclear fusion temperature

Thermodynamic Laws and Temperature

1

Zeroth Law of Thermodynamics: If two systems are each in thermal equilibrium with a third system, they are in thermal equilibrium with each other. This establishes temperature as a fundamental property and allows temperature measurement.

2

First Law of Thermodynamics: Energy cannot be created or destroyed, only converted from one form to another. In thermodynamic equations, temperature appears in calculations of internal energy and heat transfer: ΔU = Q - W.

3

Second Law of Thermodynamics: The entropy of an isolated system always increases over time. Temperature is crucial in entropy calculations: dS = dQ/T, where T must be in Kelvin for the equation to be valid.

4

Third Law of Thermodynamics: As temperature approaches absolute zero, the entropy of a perfect crystal approaches zero. This establishes absolute zero as a fundamental limit that cannot be reached in a finite number of steps.

Temperature Conversion Formulas

From To Formula Example
Celsius °C Kelvin K K = °C + 273.15 20°C = 20 + 273.15 = 293.15 K
Kelvin Celsius °C = K - 273.15 300 K = 300 - 273.15 = 26.85°C
Celsius Fahrenheit °F = (°C × 9/5) + 32 20°C = (20×9/5)+32 = 68°F
Kelvin Fahrenheit °F = (K - 273.15) × 9/5 + 32 300 K = (300-273.15)×9/5+32 = 80.33°F
Celsius Rankine °R = (°C + 273.15) × 9/5 20°C = (20+273.15)×9/5 = 527.67°R
Kelvin Rankine °R = K × 9/5 300 K = 300×9/5 = 540°R

Scientific Applications of Kelvin Scale

Temperature Range Kelvin (K) Celsius (°C) Applications
Ultra-low 0 - 1 K -273.15 to -272.15°C Quantum mechanics experiments, superconductivity research
Cryogenic 1 - 120 K -272.15 to -153.15°C Superconducting magnets, MRI machines, space telescopes
Very Cold 120 - 200 K -153.15 to -73.15°C Liquid nitrogen storage, cryopreservation
Cold 200 - 273.15 K -73.15 to 0°C Freezing conditions, dry ice, polar research
Temperate 273.15 - 310 K 0 to 36.85°C Everyday temperatures, biological systems
Hot 310 - 600 K 36.85 to 326.85°C Cooking, industrial processes, engine operation
Very Hot 600 - 2000 K 326.85 to 1726.85°C Metal melting, glass production, combustion
Extreme 2000 - 10,000 K 1726.85 to 9726.85°C Plasma research, welding arcs, lightning
Stellar 10,000 K + 9726.85°C + Star surfaces, fusion research, astrophysics

Calculator Features:

  • Bidirectional conversion: Celsius to Kelvin and vice versa
  • Interactive absolute temperature slider (0K to 500K)
  • Includes Fahrenheit and Rankine temperature scales
  • Absolute temperature scale visualization
  • Scientific temperature examples for quick reference
  • Thermodynamic constants and reference points
  • Mobile-friendly interface with responsive design

Frequently Asked Questions

Kelvin is used in scientific contexts because it is an absolute temperature scale with its zero point at absolute zero. This makes it ideal for thermodynamic equations where ratios of temperatures are needed. For example, in the ideal gas law (PV = nRT) and entropy calculations (ΔS = Q/T), temperature must be in absolute units (Kelvin) for the equations to be valid. Celsius, being a relative scale with an arbitrary zero point, would give incorrect results in these calculations.

The value 273.15 represents the difference between the zero points of the Celsius and Kelvin scales. Absolute zero (0 K) is -273.15°C. This value was determined experimentally through gas law measurements. Interestingly, since 2019, the Kelvin scale has been redefined based on the Boltzmann constant (k = 1.380649×10⁻²³ J/K), but the size of the Kelvin unit remains the same as the Celsius degree, and 0 K still equals -273.15°C.

Under normal circumstances, temperatures cannot be negative in Kelvin because it's an absolute scale starting at absolute zero. However, in certain specialized quantum systems with population inversion (like lasers), negative absolute temperatures can be defined theoretically. These aren't "colder" than absolute zero but represent systems where higher energy states are more populated than lower ones. In practical terms and for everyday science, Kelvin temperatures are always positive.

Both Kelvin and Rankine are absolute temperature scales starting at absolute zero. The difference is their unit size: Kelvin uses the same degree size as Celsius (1 K = 1°C), while Rankine uses the same degree size as Fahrenheit (1°R = 1°F). So 0 K = 0°R = absolute zero, but the conversion is: °R = K × 9/5. Kelvin is used worldwide in science, while Rankine is occasionally used in some engineering fields in the United States, particularly in thermodynamics when working with Fahrenheit-based systems.

The triple point of water (where solid, liquid, and vapor phases coexist in equilibrium) occurs at 0.01°C (273.16 K) at a pressure of 611.657 Pa. This is slightly above the normal freezing point of water (0°C at 1 atm) due to pressure differences. Since 2019, the Kelvin has been defined by fixing the numerical value of the Boltzmann constant, but the triple point of water remains an important reference point. The freezing point of water at standard atmospheric pressure is 0°C (273.15 K), which is 0.01 K lower than the triple point.