Introduction to temperature - including Celsius, Fahrenheit, Kelvin and Rankine definitions - an online temperature converter

Temperature (sometimes called thermodynamic temperature) is a measure of the average kinetic energy of the particles in a system. Temperature is the degree of "hotness" ( or "coldness") - a measure of the heat intensity.

When two objects of different temperatures are in contact - the warmer object becomes colder while the colder object becomes warmer. This means that heat flows from the warmer to the colder object.

Temperature Converter

Convert between oC (Celsius), oF (Fahrenheit), K (Kelvin) and oR (Rankine) with the calculator below:


oC oF K oR

Temperature Converter - Web App

   Temperature Converter App

Add the Temperature Converter Web App to your mobile device or desktop. The App is saved in your browser and works offline automatically after first visit.

Degree Celsius (oC) and Degree Fahrenheit (oF)

A thermometer can help us determine how cold or hot a substance is. Temperature is in most of the world measured and reported in degrees Celsius (oC). In the U.S. it is common to report temperature in degrees Fahrenheit (oF). In the Celsius and Fahrenheit scales the temperatures where ice melts (water freezes) and water boils are used as reference points.

  • In the Celsius scale the freezing point of water is defined as 0 oC and the boiling point is defined as 100 oC
  • In the Fahrenheit scale the water freezes at 32 oF and boils at 212 oF

In the Celsius scale there are 100 degrees between the freezing point and the boiling point of water compared to 180 degrees in the Fahrenheit scale. This means that 1 oC = 1.8 oF (check the section about temperature differences below).

Values can be converted between the two temperature units by using the equations:

tF = 1.8 tC + 32

   = 9/5 tC + 32                                      (1)

tC = 0.56 (tF - 32)

    = 5/9 (tF - 32)                                     (2)


tC = temperature (oC)

tF = temperature (oF)

Temperature - Celsius versus Fahrenheit diagram

Comparing Celsius and Fahrenheit:

-20 -4
-15 5
-10 14
-5 23
0 32
5 41
10 50
15 59
20 68
25 77
30 86
35 95
40 104
45 113
50 122

Example - A patient with SARS (Severe Acute Respiratory Syndrome) has a temperature of 106 oF. What is the temperature in Celsius?

tC = 5/9 ((106 oF) - 32)

    = 41.1 oC

Temperature Conversion Table - oC vs oF

Temperature - Celsius vs Fahrenheit conversion table

Temperature Difference - or Temperature Change - degree Celsius versus degree Fahrenheit

Note that for temperature difference (change) - as used in heat loss diagrams

  • 1 degree Celsius of temperature difference equals 1.8 degree Fahrenheit of temperature difference

dtC = 0.56 dtF                             (3)

dtF1.8 dtC                              (3b)


dtF = temperature difference (oF)

dtC = temperature difference (oC)

Example - Temperature Difference between 100 oC to 50 oC

Temperature difference in degrees Celsius:

dtC = (100oC) - (50oC)

              = 50 (oC)

Temperature difference in degrees Fahrenheit calculated by using (1)

tF(100oC) = 1.8 (100 oC) + 32

              = 212 oF

tF(50oC) = 1.8 (50 oC) + 32

            = 122 oF

dtF = tF(100oC) - tF(50oC)

      = 90 (oF)

Temperature difference in degrees Fahrenheit calculated by using (3)

dtF = 1.8 (50 oC)

     = 90 oF

Kelvin - K

Another scale (common in science) is Kelvin, or the Absolute Temperature Scale. On the Kelvin scale the coldest temperature possible, -273 oC, has a value of 0 Kelvin (0 K) and is called the absolute zero. Units on the Kelvin scale are called Kelvins (K) and no degree symbol is used.
Because there are no lower temperatures than 0 K  - the Kelvin scale does not have negative numbers.

The Kelvin has the same incremental scale as the Celsius scale and one unit Kelvin is equal in size to one unit Celsius:

1 unit Kelvin  = 1 unit oC

To calculate a Kelvin temperature, add 273 to the Celsius temperature:

tK = tC + 273.16                        (4)

Example - What is the normal body temperature of 37 oC in the Kelvin scale?

tK = tC + 273.16 = (37 oC) + 273.16

    = 310.16 K

Degree Rankine - R

In the English system the absolute temperature is in degrees Rankine (R), not in Fahrenheit:

tR = tF + 459.67                       (5)

Related Topics

Related Documents

Matched Content

Tag Search

  • en: temperature celsius fahrenheit kelvin
  • es: temperatura Fahrenheit Centígrados Kelvin
  • de: Temperatur Celsius Fahrenheit Kelvin

Search the Engineering ToolBox

- "Search is the most efficient way to navigate the Engineering ToolBox!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!