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Temperature Units

Updated on September 29, 2010

What is temperature?

Temperature is a measure of average heat of the thing. Average heat is the degree of hotness or coldness of that object.

For example the temperature of human body, temperature of boiled water, etc.

The common notions of temperature is hot and cold. If we hold ice, we sense cold; it means the ice has lower temperature with our body.

From physic concept, temperature is the measure of the average kinetic energy of the molecules. Each time molecule moves there will a kinetic energy. Hot means molecules move faster so the kinetic energy is increasing. Cold means molecules move slower so the kinetic energy is decreasing.

Temperature Unit

Temperature unit is a unit of measurement of temperature. The basic unit of SI (International Standard) is Kelvin (K). Kelvin unit is referenced the absence of thermal energy or absolute zero. Absolute zero is defined as Zero degree Kelvin (0K). 0K means it has no thermal energy at all.

There are many other temperature units like Fahrenheit, Celsius, and Reamur. Fahrenheit commonly used for temperature measurement in US. Celsius is used almost in every countries except US.

Celcius Scale
Celcius Scale


Celsius temperature scale is used for practically all purposes almost in every countries throughout the world. This scale was devised by the Swedish astronomer Anders Celsius

Celsius related to the temperature of water. Zero Degree Celsius (0 °C) corresponds to the temperature of water freezes. 100 °C corresponds to boiling point of water at sea level under normal atmospheric pressure.

Based on International Standard, Celsius is defined by these two points:

  • The triple point of water is defined as 0.01 oC.
  • One degree Celsius equals the change of temperature with one degree on the ideal gas-scale.

0 K (Absolute zero) is defined as being precisely as -273.15 °C. The temperature value of the triple point of water is defined as being precisely 0.01 °C. It means:
-273.15 °C = 0 K
0 °C = 273.15 K


Although Celsius has been replaced this scale in most countries. Some countries still use this scale. Fahrenheit is widely used in US and Belize. This scale is devised by Daniel Fahrenheit.

The zero point is determined by placing the thermometer in brine (a mixture of ice, water, and ammonium chloride, a salt). At standard atmospheric pressure, the freezing point of water is 32 °F and the boiling point 212 °F.

The absolute zero (0 K) is -459.67 °F

Temperature Conversion Formula


[°C] = ([°F] - 32) × 5/9
[°C] = [K] - 273.15


[°F] = [°C] × 9/5 + 32
[°F] = [K] × 9/5 - 459.67


[K] = [°C] + 273.15
[K] = ([°F] + 459.67) × 5/9

Temperature Conversion Table

Conversion to SI units
degree Celsius
C = K - 273.15
[K] = [°C] + 273.15
degree Delisle
[K] = 373.15 - [°De] x 2/3
degree Fahrenheit
F = °C x 9/5 + 32
[K] = ([°F] + 459.67) x 5/9
degree Newton
[K] = [°N] x 100/33 + 273.15
degree Rankine
R; °Ra
R = K x 9/5
[K] = [°R] x 5/9
degree Réaumur
[K] = [°Ré] x 5/4 + 273.15
degree Rømer
[K] = ([°Rø] - 7.5) x 40/21 + 273.15
kelvin (SI base unit)
= 1/273.16 of the thermodynamic temperature of the triple point of water.
= 1 K

Common temperatures

Absolute zero
0 K
-273.15 °C
-459.67 °F
Temperature of Liquid Nitrogen
77.4 K
-195.8 °C
-302.4 °F
Temperature of dry ice
195.1 K
-78 °C
-108.4 °F
Melting point of ice (approximate)
273.15 K
0 °C
32 °F
Waters triple point
273.16 K
0.01 °C
32.018 °F
Normal human body temperature
310.15 K
37.0 °C
98.6 °F
Waters boiling point at 1 atm (101.325 kPa)
373.1339 K
99.9839 °C
211.9710 °F


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      Bill 5 years ago

      use this formula instead

      F to C ((Tf + 40)*5/9) -40 = Tc

      C to F ((Tc + 40)*9/5) -40 = Tf

      these two measurement scales have different distances between the boiling and freezing points of water. These two scales are not parallel and intersect at -40.