Kelvin to Celsius Converter

Convert kelvin to Celsius (K to °C)

To convert kelvin to Celsius, subtract 273.15 from the kelvin value. It helps when reading physics and chemistry problems, cryogenic data, star temperatures or colour-temperature ratings in everyday terms. This kelvin to celsius converter works both ways: type kelvin or Celsius into either box above and the other box, the worked formula and the chart below update as you type.

The kelvin (K) is the SI base unit of temperature, named after Lord Kelvin (William Thomson). Its zero is absolute zero, the coldest temperature possible, and one kelvin is the same size as one degree Celsius. Kelvin is used in physics, chemistry, astronomy and cryogenics, and on light-bulb packaging to describe colour temperature — about 2,700 K for warm white and 6,500 K for daylight. Absolute zero, 0 K, is −273.15 °C, and each kelvin is the same size as a Celsius degree.

The degree Celsius (°C) is named after the Swedish astronomer Anders Celsius, who proposed a 100-degree scale in 1742. Water freezes at 0 °C and boils at about 100 °C at sea level, and the scale is now formally defined from the kelvin. Water freezes at 0 °C, which is 273.15 K. Celsius is the everyday scale for weather, cooking and medicine in nearly every country.

How to convert kelvin to celsius with this tool

1. Type a number into the Kelvin (K) box — it starts at 300 K as an example.
2. Read the answer in the Celsius (°C) box and in the result panel, which also shows the formula with your number.
3. To go the other way, type into the Celsius box, or press the swap button to open the Celsius to Kelvin converter with your value carried over.
4. Choose how many decimal places you want, or tap a quick value such as 0 K, 77 K, 273.15 K.
5. Press Copy result to paste the conversion into a message, spreadsheet or note.

Kelvin to Celsius converter features

Kelvin to Celsius formula

The formula is °C = K − 273.15. It is exact because the degree Celsius is defined as the kelvin offset by exactly 273.15.

The reverse formula is K = °C + 273.15 — or use the Celsius to Kelvin converter. Three worked examples:

• A 300 K lab sample: 300 − 273.15 = 26.85 °C
• Liquid nitrogen (77 K): 77 − 273.15 = −196.15 °C
• The Sun’s surface (about 5,772 K): 5,772 − 273.15 = 5,498.85 °C

Notable temperatures in kelvin

• Absolute zero: 0 K = −273.15 °C
• Liquid nitrogen boils (approx.): 77 K = −196.15 °C
• Water freezes: 273.15 K = 0 °C
• Room temperature: 293.15 K = 20 °C
• Water boils at sea level: 373.15 K = 100 °C
• The Sun’s surface (approx.): 5,772 K = 5,498.85 °C

Because the kelvin and the Celsius degree are the same size, a change of 10 K is exactly a change of 10 °C.

Kelvin to Celsius quick reference

The values people look up most often, worked out with the exact factor:

• 0 K = −273.15 °C
• 77 K = −196.15 °C
• 273.15 K = 0 °C
• 293.15 K = 20 °C

Quick tip: Subtract 273.15. For a rough reading, subtract 273: 293 K is about 20 °C (exactly 19.85 °C).

Related conversions: Fahrenheit to Celsius, Celsius to Fahrenheit and the full temperature converter.

Kelvin to Celsius conversion table

Values in Celsius are rounded to 2 decimal places (more for very small numbers). For any value not listed, type it into the converter above.