Celsius to Kelvin Formulas – How to Convert Celsius (C) to Kelvin (K)?

Posted on May 28th, 2021
Celsius to Kelvin , how to convert celsius to kelvin
Celsius to Kelvin

How to Convert Celsius to Kelvin? Celsius (C) to Kelvin (K) Formulas

Define Celsius

Celsius, commonly known as centigrade, is a temperature scale that ranges from 0° to 100° for the freezing point of water and from 0° to 100° for the boiling point of water. It was invented in 1742 by the Swedish astronomer Anders Celsius and is sometimes referred to as the centigrade scale due to the 100-degree interval between the defined points.

The following formula is used for converting a temperature from the Fahrenheit (°F) representation to a Celsius (°C) value:

0C = 5/9(0F-32)


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The Celsius scale is widely utilized everywhere the metric system of units is adopted, and it is widely employed in scientific activity.

Celsius calculated the boiling point of water to be 0° and the melting point of snow to be 100°. This was then inversed to have 0° on the cold end and 100° on the hot end, and it became widely used in that form.

Define Kelvin

Kelvin (K), the International System of Units (SI) is the base unit of thermodynamic temperature measurement. Originally, this unit was defined as  of the triple point of pure water (equilibrium between the solid, liquid, and gaseous phases).

The kelvin is also the fundamental unit of the Kelvin scale, which was named after the British physicist William Thomson (also known as Lord Kelvin). Absolute temperature scales contain absolute zero as their zero point (−459.67° on the Fahrenheit temperature scale and −273.15° on the Celsius temperature scale), which is the theoretical temperature at which the molecules of a substance have the least energy; hence, on such a scale, all values are non-negative.

Several physical laws and formulas can be represented more clearly while using an absolute temperature scale; thus, for scientific temperature measurement, the Kelvin scale has been accepted as the international standard. In both the Kelvin and Celsius scales, the difference between the freezing and boiling points of water is 100 degrees; consequently, the Kelvin degree has the same magnitude as the Celsius degree.

What is Absolute Temperature?

The universe has a minimum temperature. That is not clear in the absence of a more accurate physical interpretation of temperature.

Experiments measuring pressure v/s temperature at constant volume and mass get the same results. Typically, the slopes of the P – T graphs for various gases vary, but they always extrapolate to the same temperature for zero pressure as the V – T plots did for zero volume. Since the least possible pressure is 0, the temperature intercept represents the lowest temperature imaginable. This is known as absolute zero.

The experiments served as the foundation for the Kelvin scale. It is not arbitrary, but it is meant to have absolute zero point.

0K =  2730C = – 459.670F

The kelvin (K) is the authorized metric unit of temperature. Note that there is no “degree” with the kelvin. 3K, for e.g., is abbreviated as “three kelvins”.

The Celsius to kelvin conversion:  T =  T (0C) + 273.15

The Kelvin to Celsius conversion:  T (0C) =  T  –  273.15

One Celsius degree and one kelvin are precisely the same on the Kelvin scale.

Conversion Formulas

The list of conversion formulas is as follows:

Celsius to Kelvin,

K= C+273.15

Celsius to Fahrenheit,

F= (9/5)C + 32

Fahrenheit to Celsius,

C = 5/9(F-32)

Fahrenheit to Kelvin,

K = 5/9(F+459.67)

Fahrenheit to Rankin,

R = F + 459.67

Rankin to Kelvin,

K = (5/9)R


SI system: Basic Units

Celsius and Fahrenheit

Temperature is measured using three scales: the Kelvin, Celsius and Fahrenheit scale. The Celsius scale is known as the centigrade scale, which is an outmoded phrase.

i. Kelvin is the basic unit of temperature in the SI system, and it may be impractical under many circumstances.

ii. Because of the units are of comparable magnitude, both Kelvin and Celsius scales are interlinked, and conversion is straightforward. However, in many clinical laboratories, the most commonly used scale is Celsius scale.

iii. The theoretical temperature with no heat loss is absolute zero, and on Kelvin scale, it is represented by the zero point, which is the difference between the Kelvin scale and Celsius scale.

iv. Since the degree magnitude is same for both the scales, and on the Celsius scale, the freezing point of pure water is the zero point.

Thus, water freezes at 273 K, 0 degrees Celsius equals 273 K (kelvins) and that 0 K equals -273 degree celsius. However, to convert from kelvin to degree Celsius, add 273, and to convert from degrees celsius to kelvin, subtract 273.

K =  0C+273


0C=  K-273

Because the Celsius scale was designed with the boiling point of pure water 100oC in mind, the boiling point on the Kelvin scale is 373K.

The table below compares measurements from the three temperature scales using common reference points.

Reference point Kelvin Degrees Fahrenheit Degrees Celsius
Boiling point of water 373 212 100
Body temperature 310 98.6 37
Room temperature 293 68 20
Freezing point of water 273 32 0
Absolute zero 0 -459 -273

Similarly, the temperature was not considered a fundamental unit of measurement until quite recently. It is currently regarded as one of the seven fundamental units of measurement. Simply said, the temperature is a measure of an object’s relative “hotness” or “coldness”.

Important things to remember

i. The conversion of Celsius to Kelvin: K =  0C+273. In a pace of 273.15, the value of 273 will be taken.

ii. The particles stop moving at 0 Kelvin, i.e., -273 degrees Celsius, and the entire disturbance vanishes. Hence, nothing on the Kelvin scale can be colder than absolute zero. In the laboratory, scientists have created an atomic gas with negative Kelvin values.

iii. Kelvin is a unit of temperature, 0 degrees denotes the absence of kinetic energy or temperature. Because the scales do not begin at zero, changes in Celsius or Fahrenheit are not directly connected to kinetic energy or volume. Kelvin scale is used by the researchers because it is an absolute scale of temperature that is directly related with volume and kinetic energy.

iv. The kelvin, unit of thermodynamic temperature, is the 1/273.16 fraction of the triple point of water’s thermodynamic temperature. The kelvin and the degree Celsius are both the units of the 1990 International Temperature Scale (ITS-90), which the CIPM was introduced in 1989.

Must check:

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