What is a Fahrenheit Degree

The Fahrenheit degree (° F) is a temperature unit proposed by Gabriel Fahrenheit in 1724. The Fahrenheit degree is not a unit of the International System of Units.

On the Fahrenheit scale, the temperature changes in the state of water are as follows:

  1. The melting point of water is 32 degrees F.
  2. The boiling point of water is 212 degrees F.

A difference of 1.8ºF is equivalent to that of 1 degree Celsius . Fahrenheit adjusted the temperature to zero (0 ° F), at the freezing point of a 50% mixture of salt (ammonium chloride) and ice, and at 96 ° F, he measured the temperature of the blood (used that of the horses)

Figure 96 may seem a strange measure, but, in principle, the scale contained only twelve equal subdivisions, he himself divided each division into eight more, finally obtaining 96 divisions on his scale.

The conversion formulas for degrees Celsius and kelvin are:

° F = ° C⋅ (9/5) +32
° C = (° F -32) ⋅ 5/9
° F = K ° (9/5) -459.67
k = (° F +459.67) ⋅ 5/9


The Fahrenheit scale is officially used in five countries:

  • Bahamas.
  • Belice.
  • Cayman Islands.
  • Palace.
  • USA.

In addition, this unit is also unofficially used by the older generation in the United Kingdom, Australia, South Africa, Canada, Ireland, India and Jamaica. The reason is that this scale has also been used in these countries in the past. In other countries, the temperature is expressed in degrees Celsius , created 20 years later.

This scale is currently confined to Anglo-Saxon countries, especially the United States. The other Anglo-Saxon countries, however, are adapting to degrees Celsius, since since the 1960s, some governments have adopted policies with a tendency to adopt the International System and the use of ºF for temperature measurement has been replaced. .

The Fahrenheit scale, has absolute zero located at -459.67 ° F, to facilitate its scientific use, the Rankine scale was created. The Rankine scale raises 0 from the Fahrenheit scale to absolute zero, similar to what happens between the Kelvin scale and the Celsius scale .


Daniel Fahrenheit was a physicist, engineer and glassblower of Polish origin. He is the physicist responsible for creating the scale that bears his name to measure the temperature. He is also known for the invention of the alcohol thermometer (1709), mercury thermometer (1714) and the development of a scale to measure temperatures .

He is a pioneer of accurate thermometry, which helped lay the foundation for the era of precision thermometry, inventing the glass tube mercury thermometer and the Fahrenheit scale. Fahrenheit’s inventions marked the beginning of the first revolution in the history of thermometry. From the beginning of the 1710s until the beginning of the electronic age, glass and mercury thermometers were among the most reliable and accurate thermometers ever invented.


Fahrenheit himself wrote in 1724 that, on his scale, 0º corresponded to the temperature of a mixture of ice, salt and water, while 100º was the body temperature of the human being. We can see that the temperature in these two environments is not completely accurate, so the Fahrenheit scale is considered quite arbitrary.

It is not known exactly how it was designed, as the German physicist and engineer kept his formulas a secret.

Fahrenheit was based on the Rømer scale, proposed by the Danish astronomer Ole Christensen Rømer in 1701. According to this scale, 0 ° was the freezing temperature of the brine and 60 ° the boiling point of the water. The problem was that other important points, such as body temperature, were converted into fractional numbers, which seemed quite inelegant to him. Fahrenheit decided to adjust the Rømer scale so that the water would freeze at 8º and the human body temperature would be 24º.

The first Fahrenheit thermometers used this scale, but at some point he decided to multiply the number of divisions by 4, giving rise to the current Fahrenheit scale, where the water freezing point is 32ºF and the body temperature is 96ºF. It is not clear why he did this, but the fact is that he agrees that a degree Fahrenheit increases the volume of mercury by exactly 0.01%.


Daniel Gabriel Fahrenheit is also responsible for the invention of the mercury thermometer. Fahrenheit knew that mercury was a better measuring liquid than alcohol used in other thermometers, as it boiled at a much higher temperature (357 ° C versus 78 ° C). His thermometers became the most reliable at the time and, for these achievements, he was formally accepted into the Royal Society of London.

Leave a Comment