Celsius to Kelvin

Convert Celsius to Kelvin instantly for scientific calculations.

How to Use

1

Enter the Celsius temperature

Type the temperature in °C. Supports negative values (e.g., -273.15 for absolute zero).

2

View the Kelvin result

The Kelvin equivalent appears using K = °C + 273.15. Kelvin values are always ≥ 0.

3

Use in calculations

Apply the Kelvin value in physics equations, gas laws, or scientific documentation.

4

Convert series

Enter multiple Celsius values to convert a set of temperatures for lab reports or research.

How to convert Celsius to Kelvin

The conversion from Celsius to Kelvin is straightforward: simply add 273.15 to your Celsius temperature. Kelvin is an absolute temperature scale used primarily in science.

Formula

Kelvin = Celsius + 273.15

Common Temperature Conversions

  • 0°C = 273.15 K
  • 20°C = 293.15 K
  • 37°C = 310.15 K
  • 100°C = 373.15 K

Frequently Asked Questions

What is Kelvin used for?

Kelvin is the SI unit for absolute temperature and is used in scientific research, physics, chemistry, and engineering. It eliminates negative values and is essential for calculations involving gas laws and thermodynamics.

Why add 273.15 and not 273?

Absolute zero (0 K) equals -273.15°C precisely. The addition of 273.15 is the exact conversion. Some sources use 273 for approximations.

Real-World Examples & Use Cases

Physics & Chemistry Calculations

Kelvin is mandatory for most physics and chemistry equations because it is an absolute temperature scale. The Ideal Gas Law (PV = nRT) requires temperature in Kelvin for correct results. At 25°C (298.15 K), a gas behaves predictably — but plugging in 25 (Celsius) instead of 298.15 (Kelvin) into gas law equations produces catastrophically incorrect results. Students solving thermodynamics problems, chemists calculating reaction equilibria, and engineers designing thermal systems must convert Celsius measurements to Kelvin for any formula that uses temperature ratios.

Materials Science & Cryogenics

Extreme temperature work — studying superconductivity near absolute zero, handling liquid helium (-269°C = 4 K), or processing ceramics in high-temperature furnaces (1,400°C = 1,673 K) — requires Kelvin for SI compliance. Materials scientists, cryogenic engineers, and nanotechnology researchers document all temperature data in Kelvin for international publication. The transition temperature of superconductors, the Curie point of magnetic materials, and phase transition temperatures are all recorded in Kelvin in scientific literature.

Astronomy & Astrophysics

Stellar temperatures are measured in Kelvin because Celsius would give awkward huge numbers and no intuitive zero reference for energy comparisons. The Sun's surface temperature is approximately 5,778 K (5,504.85°C). Background radiation temperature, star classification by color and temperature (O, B, A, F, G, K, M classes), and black hole Hawking radiation temperature all use Kelvin. Space science students and amateur astronomers converting Celsius measurements to Kelvin for assignment submissions or telescope data analysis need this conversion regularly.

Color Temperature in Photography & Lighting

Color temperature — the warmth or coolness of light — is measured in Kelvin for cameras, monitors, and studio lighting. A candle flame is approximately 1,800 K; standard daylight is around 5,500-6,500 K; overcast sky is 7,000 K. Photographers setting white balance, videographers calibrating LED lighting panels, and cinematographers matching light sources on set work exclusively in Kelvin color temperature. While these aren't thermodynamic temperatures, they derive from the Kelvin temperature scale's absolute zero reference.

How It Works

The Celsius-to-Kelvin conversion is the simplest of all temperature conversions because both scales use the same interval size — one Kelvin equals one Celsius degree in magnitude. The conversion formula: K = °C + 273.15 The only difference between the scales is the zero point: - Celsius zero (0°C): defined as the freezing point of water - Kelvin zero (0 K): defined as absolute zero (the coldest theoretically possible temperature) Absolute zero in Celsius = -273.15°C, so systematically: K = °C + 273.15 The reverse: °C = K - 273.15 Key scientific reference temperatures: - Absolute zero: 0 K = -273.15°C - Water freezes: 0°C = 273.15 K - Room temperature: 20°C = 293.15 K - Body temperature: 37°C = 310.15 K - Water boils: 100°C = 373.15 K

Frequently Asked Questions

Why is Kelvin used in science instead of Celsius?▼
Kelvin is the SI base unit for temperature and has an absolute zero reference (0 K = no molecular motion). This makes temperature ratios physically meaningful in thermodynamic equations. You can say one state has 'twice the thermal energy' (in Kelvin), but not in Celsius since 0°C is arbitrary. All major physics and chemistry formulas requiring temperature use Kelvin.
What is room temperature in Kelvin?▼
Standard room temperature (20°C) equals 293.15 K. Scientific standard temperature (called STP) is 0°C (273.15 K) or sometimes 25°C (298.15 K) for thermodynamic tables. Experiment conditions stated in Kelvin specify an absolute temperature reference.
What is absolute zero and can it be reached?▼
Absolute zero is 0 K (-273.15°C) — the temperature at which all molecular thermal motion ceases. The third law of thermodynamics states that absolute zero can be approached but never actually reached. Scientists have cooled materials to within billionths of a Kelvin above absolute zero, but thermodynamic law prevents achieving the exact zero point.
Can Kelvin be negative?▼
No. Kelvin is an absolute scale starting from the lowest possible temperature. 0 K is the coldest possible state; all temperatures in Kelvin are positive. Negative Kelvin does not correspond to any physical temperature. Celsius and Fahrenheit can be negative because their zeros are defined at arbitrary reference points.
What is the Kelvin symbol and format?▼
Kelvin uses the symbol K (not °K). Unlike Celsius (°C) and Fahrenheit (°F), Kelvin does not use the degree symbol. You write '273.15 K' without a degree sign. This convention was established to distinguish it as an absolute thermodynamic scale rather than a relative degree-based scale.
Why is the offset 273.15 and not a round number like 273?▼
0 K (absolute zero) is -273.15°C precisely based on measurements. The exact value emerged from thermodynamic experiments and the ideal gas temperature scale. Some textbooks and quick calculations use 273 as an approximation, introducing a 0.15°C error. For scientific accuracy, always use 273.15.

Related Tools

Explore other tools in this category.

Length Converter

Easily convert between different units of length including centimeters, inches, feet, meters, and miles.

Area & Volume Converter

Convert between area units (m², ft², acre) and volume units (L, gal, m³) instantly.

Temperature Converter

Convert between Celsius, Fahrenheit, Kelvin, and Rankine instantly.

Data Size Converter

Convert between bits, bytes, KB, MB, GB, TB, PB and IEC binary units (KiB, MiB, GiB).

Speed Converter

Convert between m/s, km/h, mph, knots, fps, Mach, and the speed of light instantly.

Fuel Efficiency Converter

Convert between MPG (US/UK), L/100km, km/L, and more fuel efficiency units.

Looking for something else?

More in this CategoryExplore All Tools