Degrees Celsius to kelvins
To convert degrees Celsius to kelvins, use the formula K = °C + 273.15.
20 °C = 293.15 K
How to convert degrees Celsius to kelvins
The kelvin is the SI base unit of temperature, fixed since 2019 by defining the Boltzmann constant as exactly 1.380649×10⁻²³ J/K — 0 K is absolute zero. The degree Celsius is the Celsius scale, defined through the kelvin as t/°C = T/K − 273.15; it was originally calibrated so that water froze at 0 °C and boiled at about 100 °C at 1 atm.
Worked example — 20 °C converts to 293.15 K using K = °C + 273.15.
Degrees Celsius to kelvins table
| Degrees Celsius | Kelvins |
|---|---|
| -273.15 °C | 0 K |
| -40 °C | 233.15 K |
| 0 °C | 273.15 K |
| 20 °C | 293.15 K |
| 25 °C | 298.15 K |
| 37 °C | 310.15 K |
| 100 °C | 373.15 K |
Reverse and related
About degrees Celsius and kelvins
Degree Celsius (°C)
Definition. The Celsius scale, defined through the kelvin as t/°C = T/K − 273.15; it was originally calibrated so that water froze at 0 °C and boiled at about 100 °C at 1 atm
History and origin
The Celsius scale was proposed by the Swedish astronomer Anders Celsius in 1742, originally with 0 for boiling and 100 for freezing; the scale was soon reversed to the familiar form. It is now defined through the kelvin, with a temperature in degrees Celsius equal to the same temperature in kelvin minus 273.15.
Current use
Celsius is the everyday temperature scale almost everywhere for weather, cooking and body temperature; the United States is the main exception, using Fahrenheit.
Source: BIPM, The International System of Units (SI), 9th ed. (2019)
Kelvin (K)
Definition. The SI base unit of temperature, fixed since 2019 by defining the Boltzmann constant as exactly 1.380649×10⁻²³ J/K — 0 K is absolute zero
History and origin
The kelvin is named after William Thomson, Lord Kelvin, who proposed an absolute temperature scale in 1848 starting from absolute zero. Since 2019 it has been defined by fixing the Boltzmann constant, tying temperature directly to energy.
Current use
The kelvin is the scientific temperature unit used in physics and engineering, and also describes the colour temperature of light sources.
Source: BIPM, The International System of Units (SI), 9th ed. (2019)
Where people use this
Degrees Celsius: weather outside the US, cooking, body temperature. Kelvins: science and physics, colour temperature. 0 °C is 273.15 K; a change of 1 °C is a change of 1 K.
The Celsius and Kelvin scales rise in the same steps — a change of 1 °C is a change of 1 K — but Kelvin starts at absolute zero, which is −273.15 °C, so the two differ only by that fixed offset of 273.15.
Every value is carried to full double precision; the display is rounded.
Both units are defined in BIPM, The International System of Units (SI), 9th ed. (2019).
Questions people ask
How do you convert Celsius to Kelvin?
Add 273.15: K = °C + 273.15. The step size is the same on both scales.
What is 25 °C in Kelvin?
25 °C is 298.15 K.
What is absolute zero in Celsius?
Absolute zero, 0 K, is −273.15 °C.