The extent of hotness or coldness of an object or a body is referred to as Temperature. In scientific terms, it is the measure of the mean kinetic energy of the inordinate motions of the particles present in a certain system. The importance of temperature in our daily lives cannot be overemphasized; it is vital in our everyday lives and in several fields such as medicine, natural sciences, among others.

We appreciate the temperature of a place or body with the use of a thermometer. They are calibrated in one or more temperature scales. Around the globe, there are three prominent temperature scales; Celsius scale (previously referred to as *centigrade*, denoted as °C), Kelvin scale (denoted as K) and Fahrenheit scale (denoted °F). However, the International System of Units (SI) which has 7 fundamental quantities, among which is temperature utilizes the Kelvin scale (k). This scale is extensively utilized in sciences and technology.

**Background of Temperature Scales**

Even though there are several temperature scales, the most common ones are the Fahrenheit, Celsius and Kelvin. Temperature values can be converted from one temperature scale to another using formula and other methods. However, you must first of all understand how the scales were invented and what they measure so you can easily convert from one scale to another.

The Fahrenheit scale was invented by Daniel Gabriel Fahrenheit, a physicist from Germany in 1724. Following his invention of the mercury thermometer in 1714, he wanted to be able to measure temperature accurately. With this scale, the freezing and boiling points of water are divided into 180 degrees, taking 32 F as the freezing point of water while 212 F is assumed as the boiling point. The design of the Fahrenheit thermometer was based on that original temperature and pressure device described by Galileo. Today, the Fahrenheit scale is used primarily in the United States of America.

The Celsius temperature scale, which is oftentimes called the centigrade scale, was devised by Swedish Astronomer Anders Celsius in 1741. The word centigrade literally refers to “consisting of or divided into 100 degrees”: meaning that the Celsius scale consists of “100 degrees between the freezing point of 0 degrees and boiling point of 100 degrees of pure water at sea level air pressure, 29.92 inches of mercury”. In 1948, the International symposium on weights and measures adopted the term Celsius and it has become one of the most extensively used scales in the world.

There is a third temperature scale that is utilized by Scientists for unique measurements. This scale is referred to as the absolute or Kelvin scale. It was devised by a British Scientist, William Thomson, also referred to as Lord Kelvin. He made significant discoveries about heat and its properties in the 19^{th} century. According to scientists, it is only possible theoretically for a body to get as cold as minus 273.15 degrees Celsius. Even though this temperature has not been reached in experiments, scientists have come close. Hence, the number, minus 273.15 degrees Celsius, is referred to as the absolute zero. Scientists are of the view that molecular motion is no longer possible at this temperature, hence it is impossible to get colder than that.

While the Fahrenheit scale is mostly used in the United States, the Celsius is popular in most other Western nations, but is also used in the United States. Even though you can convert temperature values from one temperature scale to another using different online converter, it is advisable to understand how to convert one scale to the other in other to obtain accurate temperature readings.

There is another temperature scale that is utilized in specific calculations and measurements but is now obsolete. Devised by a French scientist named R A F de Raumur (1683-1757), the Raumur scale was extensively utilized in France and by scientists to make temperature measurements in the 18^{th} and 19^{th} centuries before the advent of the Fahrenheit and Celsius scales. Raumar did not utilize mercury in his work but came up with a good working thermometer. He used the freezing point of water as his zero mark, and put the boiling point at 80 degrees.

Another lesser known scale is the Rankine scale, developed by W J M Rankine (1820-1872), a Scottish engineer. However, the scale was just a Kelvin scale utilizing the Fahrenheit degree rather than the Celsius. Even though it was widely used in certain scientific communities, it does not have any practical use in other areas of measurement.

For the purpose of this article, we will look at the three most popular temperature scales: Fahrenheit, Celsius and Kelvin.

**Temperature Conversion Formulas**

The table below shows how to convert temperature values from Celsius to Fahrenheit, Kelvin to Fahrenheit, Fahrenheit to Celsius, Celsius to Kelvin, Kelvin to Celsius and Fahrenheit to Kelvin.

Celsius to Fahrenheit | ° F = 9/5 ( ° C) + 32 |

Kelvin to Fahrenheit | ° F = 9/5 (K – 273) + 32 |

Fahrenheit to Celsius | ° C = 5/9 (° F – 32) |

Celsius to Kelvin | K = ° C + 273 |

Kelvin to Celsius | ° C = K – 273 |

Fahrenheit to Kelvin | K = 5/9 (° F – 32) + 273 |

From the table, if you know the temperature in Fahrenheit and want to convert it to Celsius, you will use the formula:

**C = 5/9 x (F-32); **where C is Celsius

This entails first subtracting 32 from the temperature in Fahrenheit and multiplying the outcome by 5/9. The formula is:

To make this clearer, we will use an example.

Let’s say you want to convert 70 F to Celsius. Follow these steps:

- 70 minus 32 is 38
- 5 divided by 9 is 0.5555555555555
- Multiply the result by 38
- The answer is 21

If you use the equation,

**C = 5/9 x (F-32)**

**C = 5/9 x (70-32)**

**C = 5/9 x 38**

**C = 0.55 x 38**

**C = 20.9, which rounds to 21**

Therefore, 70 F is equal to 21^{0}C.

You can check your work by converting 21 degrees Celsius to Fahrenheit to check your work, as follows:

**9 divided by 5 is 1.8****1.8 multiplied by 21 is 37.8****37.8 plus 32 = 69.8****This is rounded off to 70F**

To convert from Celsius to Fahrenheit, using the same values, use the formula below:

**F = [(9/5)C] + 32**

**F = [(9/5) x 21] + 32**

**F = [1.8 x 21] + 32**

**F = 37.8 + 32**

**F = 69.8, rounded off to 70F**

It is also possible to convert from Celsius to Fahrenheit by using a fast approximation method. Here, you will double the temperature in Celsius, subtract 10 percent of your result and add 32.

Let’s say for example that the temperature of a European city is 19C. If you need to convert that to Fahrenheit so you will know exactly how to dress outdoors, you can do a quick conversion. First, double the 19, or 2 x 19 = 38. Then, calculate 10 % of 38 to yield 3.8, rounding it up to 4. Next, calculate: 38 – 4 = 34 and then add 34 and 32 to get 66 F. This means that all you need for going outdoors is a sweater but not a big coat.

Using another example, say the temperature of your destination is 28 C, you can then calculate the approximate temperature in Fahrenheit by following the steps below:

**Double 28 doubled = 56 (or 2 x 28 = 56)****10 percent of 56 = 5.6, which rounds to 6****56 – 6 = 50****50 + 32 = 82**

You can also use the scale to convert from Celsius to Kelvin. Firstly, it should be noted that the Kelvin scale uses this number as zero. Therefore, to obtain temperature vales in Kelvin, you have to add 273 degrees to the Celsius temperature.

Type the temperature value to be converted in the °F, °C, or °K box and click the submit button

Printable Temperature Conversion Table

Temperature Conversion Table

Wallet Size Printable Temperature Conversion Table

Great for travel, Human body temperature and general reference.

Temperature World

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