Kelvin to Celsius Converter
Quick Conversion: C = K − 273.15
Kelvin to Celsius Converter
What Is Kelvin?
The kelvin (K) is the SI base unit of thermodynamic temperature, starting at absolute zero (0 K = −273.15°C). Defined since 2019 by fixing the Boltzmann constant, it is the standard unit in physics, chemistry, engineering, and astronomy. One kelvin equals one Celsius degree in magnitude.
What Is Celsius?
The degree Celsius (°C) sets the freezing point of water at 0°C and the boiling point at 100°C. It is the most widely used temperature scale worldwide for weather, cooking, and everyday measurement. The Celsius and Kelvin scales share the same degree size — they differ only in their zero points.
Kelvin to Celsius Formula
The formula is exact:
°C = K − 273.15 exact
Simply subtract 273.15 from the kelvin value. This is the inverse of the Celsius-to-Kelvin conversion and is equally exact.
Worked Example
Convert 310.15 K (human body temperature) to Celsius:
- Subtract: 310.15 − 273.15 = 37°C
So 310.15 K = 37°C — normal body temperature. In medical research, body temperature is often reported in kelvin.
Quick Estimation
Just subtract 273 (dropping the 0.15). Example: 373 K − 273 = 100°C (exact: 99.85°C). The error of 0.15°C is irrelevant for everyday use — only matters for precision measurements.
Reference Table: Scientific Milestones
| K | °C | Significance |
|---|---|---|
| 0 | −273.15 | Absolute zero |
| 2.725 | −270.42 | Cosmic microwave background |
| 77.15 | −196 | Liquid nitrogen boils |
| 194.65 | −78.5 | Dry ice sublimes |
| 273.15 | 0 | Water freezes |
| 293.15 | 20 | Room temperature |
| 310.15 | 37 | Human body temperature |
| 373.15 | 100 | Water boils |
| 5,778 | 5,505 | Surface of the Sun |
When Would You See Kelvin in Daily Life?
While kelvin is mainly a scientific unit, it appears in everyday contexts more than you might expect:
- Light bulb color temperature: LED and photography lighting is rated in kelvin — 2700 K (warm white), 4000 K (neutral), 6500 K (daylight blue). These aren't "heat" temperatures but describe the color of emitted light.
- Cryogenics and food storage: Industrial freezing and liquid nitrogen containers (-196°C = 77 K) are sometimes specified in kelvin in technical documentation.
- Space and astronomy news: The cosmic microwave background radiation is 2.725 K. News about space discoveries often quote temperatures in kelvin.
Frequently Asked Questions
What is 0 K in Celsius?
0 K = −273.15°C. This is absolute zero — the lowest possible temperature, where molecular motion reaches its minimum. It cannot be reached in practice.
What is room temperature in Kelvin?
Room temperature (20–25°C) equals 293–298 K. The standard reference temperature in chemistry is 25°C = 298.15 K.
Is a 1 K change the same as a 1°C change?
Yes — the degree sizes are identical. A temperature change of 50 K equals exactly 50°C. The scales differ only in where zero is placed.
Can anything be colder than 0 K?
No. The third law of thermodynamics states absolute zero can be approached but never reached. The coldest recorded temperature in a lab is about 38 picokelvin (3.8 × 10⁻¹¹ K) — unfathomably close to zero but not quite there.
Temperature conversion chart
| To Fahrenheit | To Celsius | To Kelvin | |
| From Fahrenheit (F) | F | (F - 32) × 5/9 | (F - 32) × 5/9 + 273.15 |
| From Celsius (C or o) | (C × 9/5) + 32 | C | C + 273.15 |
| From Kelvin (K) | (K - 273.15) × 9/5 + 32 | K - 273.15 | K |
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All unit conversions on CoolConversion use conversion factors defined or documented by internationally recognised standards bodies (such as ISO and NIST), including both SI and non-SI units.
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