Loading Calculator...
Please wait a moment
Please wait a moment
Convert Kelvin to Celsius instantly with our free online calculator. Essential for translating scientific readings into everyday temperatures, interpreting lab data, and bridging research scales to practical use.
−273.15
°C = 0 K (Absolute Zero)
K − 273.15
Conversion Formula
1 K = 1 °C
Same Degree Size
Formula: °C = K − 273.15
| Kelvin (K) | Celsius (°C) | Context |
|---|---|---|
| 0 K | −273.15 °C | Absolute zero — coldest possible temperature |
| 2.7 K | −270.45 °C | Cosmic microwave background temperature |
| 77.36 K | −195.79 °C | Liquid nitrogen boiling point |
| 90.19 K | −182.96 °C | Liquid oxygen boiling point |
| 194.65 K | −78.5 °C | Dry ice (solid CO₂) sublimation |
| 233.15 K | −40 °C | Where Fahrenheit and Celsius are equal |
| 273.15 K | 0 °C | Water freezing point (standard pressure) |
| 293.15 K | 20 °C | Typical room temperature |
| 298.15 K | 25 °C | Standard temperature (SATP) |
| 310.15 K | 37 °C | Normal human body temperature |
| 373.15 K | 100 °C | Water boiling point (standard pressure) |
| 1,273.15 K | 1,000 °C | Common metallurgical temperature |
| 5,778 K | 5,505 °C | Surface temperature of the Sun |
Kelvin (K) is the base unit of temperature in the International System of Units (SI). Proposed by Lord Kelvin (William Thomson) in 1848, it is an absolute thermodynamic scale that begins at absolute zero (0 K) — the point at which all classical molecular motion ceases. Unlike Celsius and Fahrenheit, Kelvin does not use the degree symbol; a temperature is simply stated as "300 K," not "300 °K." The Kelvin scale is indispensable in physics, chemistry, and engineering because many fundamental equations — including the ideal gas law (PV = nRT) and the Stefan-Boltzmann radiation law — require an absolute temperature reference to produce correct results.
Celsius (°C), originally called centigrade, is a temperature scale proposed by Swedish astronomer Anders Celsius in 1742. It defines its two reference points around water: 0 °C for the freezing point and 100 °C for the boiling point at standard atmospheric pressure. The Celsius scale is the most widely used temperature scale in the world for weather reports, cooking, medicine, and general-purpose measurement. In 1948, the General Conference on Weights and Measures officially renamed the scale from "centigrade" to "Celsius."
The relationship between the two scales is elegantly simple: °C = K − 273.15. Both use identical degree increments — a temperature change of 1 K is exactly 1 °C — so conversion involves only an offset, never a multiplier. This means Kelvin readings can be translated to everyday Celsius values (and vice versa) through straightforward subtraction or addition.
The formula is: °C = K − 273.15. Simply subtract 273.15 from any Kelvin temperature to get the equivalent in Celsius. No multiplication or division is needed.
Question: A laboratory incubator is set to 310.15 K. What is this in Celsius?
Question: Liquid nitrogen boils at 77.36 K. What is its boiling point in Celsius?
Question: The Sun's photosphere averages 5,778 K. Convert to Celsius.
For a fast estimate, subtract 273 instead of 273.15. This gives an answer within 0.15 °C of the true value — accurate enough for most everyday purposes. For instance, 373 K − 273 = 100 °C (exact is 99.85 °C when using the shortcut on 373 K, but 373.15 K − 273.15 = 100 °C exactly).
| Phenomenon | Kelvin | Celsius |
|---|---|---|
| Absolute zero | 0 K | −273.15 °C |
| Cosmic microwave background | 2.7 K | −270.45 °C |
| Helium-4 boiling point | 4.22 K | −268.93 °C |
| Hydrogen boiling point | 20.28 K | −252.87 °C |
| Nitrogen boiling point | 77.36 K | −195.79 °C |
| Oxygen boiling point | 90.19 K | −182.96 °C |
| Dry ice sublimation | 194.65 K | −78.5 °C |
| Scenario | Kelvin | Celsius |
|---|---|---|
| Water freezing point | 273.15 K | 0 °C |
| Refrigerator interior | 277 K | 3.85 °C |
| Comfortable room | 293.15 K | 20 °C |
| Standard lab temperature | 298.15 K | 25 °C |
| Human body temperature | 310.15 K | 37 °C |
| Hot summer day | 313.15 K | 40 °C |
| Fever threshold | 311.15 K | 38 °C |
| Reference | Kelvin | Celsius |
|---|---|---|
| Water boiling point | 373.15 K | 100 °C |
| Lead melting point | 600.61 K | 327.46 °C |
| Wood combustion | ~573 K | ~300 °C |
| Iron melting point | 1,811 K | 1,538 °C |
| Tungsten melting point | 3,695 K | 3,422 °C |
| Surface of the Sun | 5,778 K | 5,505 °C |
| Lightning bolt | ~30,000 K | ~29,727 °C |
Lab instruments and research papers frequently report temperatures in Kelvin. Converting to Celsius helps researchers quickly understand whether a measurement represents room temperature, cryogenic conditions, or extreme heat — making data interpretation faster and more intuitive.
Many precision instruments — spectrophotometers, calorimeters, and thermal sensors — output readings in Kelvin. Lab technicians and medical professionals convert these to Celsius to align with clinical standards (e.g., body temperature of 37 °C = 310.15 K).
Physics, chemistry, and engineering students routinely convert between Kelvin and Celsius when solving thermodynamics problems, ideal gas law calculations, and heat transfer equations. Understanding this conversion is foundational to STEM education.
Astronomical temperatures — from the 2.7 K cosmic microwave background to the millions of Kelvin in stellar cores — are always expressed in Kelvin. Converting to Celsius puts these extreme values into a human-relatable context for public communication and journalism.
Unlike Fahrenheit conversions that involve multiplication and addition, the Kelvin-to-Celsius conversion is a pure offset. This makes it one of the simplest unit conversions in science.
Subtracting 273 instead of 273.15 gives a result within 0.15 °C — well within tolerance for everyday estimates and casual use.
If your Celsius result is larger than the Kelvin input, something went wrong. Celsius values are always numerically smaller (or negative) compared to their Kelvin equivalents.
K to °C requires subtraction (K − 273.15). Adding 273.15 would convert Celsius to Kelvin — the opposite direction.
The SI standard writes "K" without a degree symbol. Writing "°K" is incorrect. Celsius uses the degree sign (°C), but Kelvin does not.
Kelvin cannot be negative. If a Kelvin input is below zero, the measurement is erroneous. The lowest valid Kelvin value is 0 (absolute zero = −273.15 °C).
Subtract 273.15 from the Kelvin value. The formula is °C = K − 273.15. For example, 300 K = 300 − 273.15 = 26.85 °C. No multiplication or division is needed because one Kelvin increment equals one Celsius degree.
No. Kelvin is an absolute temperature scale that begins at absolute zero (0 K), the lowest physically possible temperature. Negative Kelvin values do not exist under classical thermodynamics.
Room temperature is typically 20-25 °C, which equals 293.15-298.15 K. Standard ambient temperature and pressure (SATP) defines room temperature as exactly 298.15 K (25 °C).
Kelvin is an absolute scale with no negative values, making it essential for thermodynamic equations, gas laws (PV = nRT), and radiation calculations (Stefan-Boltzmann law). Equations that require proportional temperature relationships only work correctly with Kelvin.
Yes. Both scales use identical degree increments. They differ only in their zero point: 0 K = −273.15 °C (absolute zero) versus 0 °C = 273.15 K (water freezing point). This is why the conversion is a simple subtraction.
Absolute zero is 0 K, which equals −273.15 °C (or −459.67 °F). It is the theoretical lower limit of temperature where particles have minimal vibrational motion. It has never been reached in practice, though scientists have cooled matter to within billionths of a Kelvin.
Normal human body temperature is about 310.15 K. Using the formula: 310.15 − 273.15 = 37 °C (98.6 °F). This conversion is common when interpreting medical sensor data that reports in Kelvin.
Key scientific temperatures include: 0 K (−273.15 °C) absolute zero, 2.7 K (−270.45 °C) cosmic microwave background, 77.36 K (−195.79 °C) liquid nitrogen boiling point, 273.15 K (0 °C) water freezing, 373.15 K (100 °C) water boiling, and 5,778 K (5,505 °C) surface of the Sun.
This calculator uses the internationally recognized offset of 273.15 between Kelvin and Celsius scales. For critical scientific measurements, laboratory calibrations, or regulatory compliance, always verify conversions against your instrument's documentation and applicable standards (e.g., ITS-90 temperature scale).