Convert Kelvin to Celsius
Instantly convert Kelvin (K) to Celsius (°C) with our free online calculator.
Formula: K to °C — K − 273.15
Reference Table
| Kelvin (K) | Celsius (°C) |
|---|---|
| 1 | -272.15 |
| 5 | -268.15 |
| 10 | -263.15 |
| 25 | -248.15 |
| 50 | -223.15 |
| 100 | -173.15 |
How to Convert Kelvin to Celsius
Formula
To convert Kelvin (K) to Celsius (°C): K − 273.15
Step-by-Step
- Start with your value in Kelvin (K).
- K − 273.15 to perform the conversion.
- The result is your value expressed in Celsius (°C).
Conversion Factor
1 K = -272.15 °C
Reverse Factor
1 °C = 274.15 K
Worked Example
Convert 25 Kelvin to Celsius: 25 K = -248.15 °C
About Kelvin (K)
The SI base unit of temperature per ISO 80000-5 §5-1, measured on an absolute scale where 0 K is absolute zero — the theoretical point at which all classical thermal motion stops (zero-point quantum motion remains). Named after Belfast-born British physicist William Thomson, 1st Baron Kelvin (1824-1907), whose 1848 paper 'On an Absolute Thermometric Scale' established the absolute-temperature concept. Redefined in 2019 BIPM SI revision by fixing the Boltzmann constant k_B = 1.380649 × 10⁻²³ J/K exactly. Kelvin shares its degree interval with Celsius (1 K = 1 °C, but offset by 273.15: 0 °C = 273.15 K), so conversion is a straight addition. Scientific publications, thermodynamic state-function math (entropy ds, free energy dG = dH - T·dS — requires absolute temperature), cryogenic physics (liquid helium boils at 4.2 K, liquid nitrogen at 77.4 K, dry ice CO₂ sublimes at 195 K), color temperature in photography and lighting (incandescent 2,700-3,000 K, daylight 5,500-6,500 K, blue sky 10,000-15,000 K), stellar surface temperatures (Sun 5,778 K; Sirius 9,940 K; Betelgeuse 3,500 K), and plasma physics (fusion plasma 10⁸ K) all use kelvin because absolute-zero-referenced math stays dimensionally clean.
About Celsius (°C)
A temperature scale on which water freezes at exactly 0 °C and boils at exactly 100 °C under standard atmospheric pressure (101.325 kPa) — devised by Swedish astronomer Anders Celsius in 1742 (originally inverted, with 0 at boiling and 100 at freezing — flipped to the modern convention by Carl Linnaeus in 1745). Celsius is the global standard for: weather forecasts and climate-change reporting (IPCC AR6 baseline 1.5 °C / 2 °C / 4 °C warming scenarios), cooking and food-safety temperatures per FDA Food Code + EU EFSA guidelines (safe cold storage <4 °C; safe meat cooking ≥74 °C internal), human body temperature (normal core 36.5-37.5 °C per WHO; fever clinical threshold ≥38 °C), HVAC thermostat settings outside US, refrigerant and process temperatures in chemical engineering per IUPAC SATP (Standard Ambient Temperature & Pressure = 25 °C, 100 kPa), and most scientific measurement worldwide outside the US. Because the Celsius degree interval is identical to the kelvin (Δ1 °C = Δ1 K), Celsius and kelvin convert via simple +/- 273.15 offset, making it the everyday face of SI temperature: scientists and laypeople alike use it without conversion penalty.
Quick Facts
- 1 Kelvin equals -272.15 Celsius
- 1 Celsius equals 274.15 Kelvin
- Kelvin is a unit of temperature
- Celsius is a unit of temperature
- This conversion is commonly used in weather forecasting, cooking, scientific experiments, and HVAC
- The Kelvin belongs to the metric system
Common Kelvin to Celsius Conversions
| Kelvin (K) | Celsius (°C) |
|---|---|
| -40 | -313.15 |
| -20 | -293.15 |
| -10 | -283.15 |
| 0 | -273.15 |
| 5 | -268.15 |
| 10 | -263.15 |
| 15 | -258.15 |
| 20 | -253.15 |
| 25 | -248.15 |
| 30 | -243.15 |
| 35 | -238.15 |
| 37 | -236.15 |
| 40 | -233.15 |
| 50 | -223.15 |
| 60 | -213.15 |
| 70 | -203.15 |
| 80 | -193.15 |
| 90 | -183.15 |
| 100 | -173.15 |
| 150 | -123.15 |
| 200 | -73.15 |
Understanding Kelvin
The Kelvin (symbol: K) is a unit of temperature. The SI base unit of temperature per ISO 80000-5 §5-1, measured on an absolute scale where 0 K is absolute zero — the theoretical point at which all classical thermal motion stops (zero-point quantum motion remains). Named after Belfast-born British physicist William Thomson, 1st Baron Kelvin (1824-1907), whose 1848 paper 'On an Absolute Thermometric Scale' established the absolute-temperature concept. Redefined in 2019 BIPM SI revision by fixing the Boltzmann constant k_B = 1.380649 × 10⁻²³ J/K exactly. Kelvin shares its degree interval with Celsius (1 K = 1 °C, but offset by 273.15: 0 °C = 273.15 K), so conversion is a straight addition. Scientific publications, thermodynamic state-function math (entropy ds, free energy dG = dH - T·dS — requires absolute temperature), cryogenic physics (liquid helium boils at 4.2 K, liquid nitrogen at 77.4 K, dry ice CO₂ sublimes at 195 K), color temperature in photography and lighting (incandescent 2,700-3,000 K, daylight 5,500-6,500 K, blue sky 10,000-15,000 K), stellar surface temperatures (Sun 5,778 K; Sirius 9,940 K; Betelgeuse 3,500 K), and plasma physics (fusion plasma 10⁸ K) all use kelvin because absolute-zero-referenced math stays dimensionally clean.
It belongs to the metric measurement system.
Kelvin are commonly used in weather forecasting, cooking, scientific experiments, and HVAC.
Understanding Celsius
The Celsius (symbol: °C) is a unit of temperature. A temperature scale on which water freezes at exactly 0 °C and boils at exactly 100 °C under standard atmospheric pressure (101.325 kPa) — devised by Swedish astronomer Anders Celsius in 1742 (originally inverted, with 0 at boiling and 100 at freezing — flipped to the modern convention by Carl Linnaeus in 1745). Celsius is the global standard for: weather forecasts and climate-change reporting (IPCC AR6 baseline 1.5 °C / 2 °C / 4 °C warming scenarios), cooking and food-safety temperatures per FDA Food Code + EU EFSA guidelines (safe cold storage <4 °C; safe meat cooking ≥74 °C internal), human body temperature (normal core 36.5-37.5 °C per WHO; fever clinical threshold ≥38 °C), HVAC thermostat settings outside US, refrigerant and process temperatures in chemical engineering per IUPAC SATP (Standard Ambient Temperature & Pressure = 25 °C, 100 kPa), and most scientific measurement worldwide outside the US. Because the Celsius degree interval is identical to the kelvin (Δ1 °C = Δ1 K), Celsius and kelvin convert via simple +/- 273.15 offset, making it the everyday face of SI temperature: scientists and laypeople alike use it without conversion penalty.
It belongs to the metric measurement system.
Celsius are commonly used in weather forecasting, cooking, scientific experiments, and HVAC.
Why Convert Kelvin to Celsius?
Converting between Kelvin and Celsius is essential for a variety of everyday and professional tasks. International recipes list oven temperatures in different scales, weather reports from other countries use unfamiliar units, and scientists must reconcile data recorded under different conventions. Medical professionals also compare body temperature readings that may be reported in different units depending on the country or device.
Frequently Asked Questions
How do I convert Kelvin to Celsius?
The SI base unit of temperature per ISO 80000-5 §5-1, measured on an absolute scale where 0 K is absolute zero — the theoretical point at which all classical thermal motion stops (zero-point quantum motion remains). To convert Kelvin to Celsius, K − 273.15. For example, 25 K equals -248.15 °C.
How many Celsius are in 1 Kelvin?
There are -272.15 Celsius in 1 Kelvin.
How many Kelvin are in 1 Celsius?
There are 274.15 Kelvin in 1 Celsius.
What is the formula for Kelvin to Celsius conversion?
The formula is: K − 273.15. This means 1 K = -272.15 °C.
Is a Kelvin bigger than a Celsius?
Yes. One Kelvin is larger than one Celsius because 1 K equals -272.15 °C, which is less than 1.
When do you need to convert between Kelvin and Celsius?
A temperature scale on which water freezes at exactly 0 °C and boils at exactly 100 °C under standard atmospheric pressure (101. Kelvin and Celsius are both temperature units, so conversion comes up whenever one source of information uses one unit and another uses the other — a classic cross-reference challenge in engineering, trade, travel, and everyday life.