# Fahrenheit facts for kids

Kids Encyclopedia Facts
Thermometer with Fahrenheit (marked on outer bezel) and Celsius (marked on inner dial) degree units

Fahrenheit (more precisely, a degree Fahrenheit) is a unit of measurement used to measure temperature. The conversion rate to Celsius is C= 5/9 x (F − 32). The degree Fahrenheit is abbreviated °F.

It continues to be officially used in the United States (including its unincorporated territories), its freely associated states in the Western Pacific (Palau, the Federated States of Micronesia and the Marshall Islands), the Cayman Islands, and Liberia. In the United Kingdom, Fahrenheit is encountered on some websites, as well as some weather forecasts; the main reason for this is because some of the older population are more familiar with Fahrenheit.

Fahrenheit is commonly still used alongside the Celsius scale in other countries that use the U.S. metrological service, such as Antigua and Barbuda, Saint Kitts and Nevis, the Bahamas, and Belize. A handful of British Overseas Territories, including the Virgin Islands, Montserrat, Anguilla, and Bermuda, also still use both scales. All other countries now use Celsius ("centigrade" until 1948), which was invented 18 years after the Fahrenheit scale.

## History

Daniel Gabriel Fahrenheit

This temperature scale was made in 1724 by a German scientist named Daniel Gabriel Fahrenheit. According to a letter Fahrenheit wrote to his friend Herman Boerhaave, his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømer scale, brine freezes at zero, water freezes and melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by 4 in order to eliminate fractions and make the scale more fine-grained. He then re-calibrated his scale using the melting point of ice and normal human body temperature (which were at 30 and 90 degrees); he adjusted the scale so that the melting point of ice would be 32 degrees, and body temperature 96 degrees, so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval 6 times (since 64 = 26).

Fahrenheit soon after observed that water boils at about 212 degrees using this scale. The use of the freezing and boiling points of water as thermometer fixed reference points became popular following the work of Anders Celsius, and these fixed points were adopted by a committee of the Royal Society led by Henry Cavendish in 1776–77. Under this system, the Fahrenheit scale is redefined slightly so that the freezing point of water was exactly 32 °F, and the boiling point was exactly 212 °F, or 180 degrees higher. It is for this reason that normal human body temperature is approximately 98.6 °F (oral temperature) on the revised scale (whereas it was 90° on Fahrenheit's multiplication of Rømer, and 96° on his original scale).

In the twentieth century, the unit declined in favour for the degree Celsius.

The use of the degree Fahrenheit is in decline throughout the majority of the world with the USA being the main exception.

The degree Fahrenheit is often considered to be "old fashioned" throughout the majority of the world as it is an older and outdated way of measuring temperature. The degree Celsius has largely replaced Fahrenheit's use as it is generally easier to use.

## Examples

On the Fahrenheit scale, water freezes at 32° and boils at 212°.

• Room temperature is about 70 °F.
• A human's body temperature is usually close to 98.6 °F.
• Absolute zero is –459.67 °F.

### Conversion (specific temperature point)

For an exact conversion between degrees Fahrenheit and Celsius, and kelvins of a specific temperature point, the following formulas can be applied. Here, f is the value in degrees Fahrenheit, c the value in degrees Celsius, and k the value in kelvins:

• f °F to c °C: c = f − 321.8
• c °C to f °F: f = c × 1.8 + 32
• f °F to k K: k = f + 459.671.8
• k K to f °F: f = k × 1.8 − 459.67

There is also an exact conversion between Celsius and Fahrenheit scales making use of the correspondence −40 °F ≘ −40 °C. Again, f is the numeric value in degrees Fahrenheit, and c the numeric value in degrees Celsius:

• f °F to c °C: c = f + 401.8 − 40
• c °C to f °F: f = (c + 40) × 1.8 − 40

### Conversion (temperature difference or interval)

When converting a temperature interval between the Fahrenheit and Celsius scales, only the ratio is used, without any constant (in this case, the interval has the same numeric value in kelvins as in degrees Celsius):

• f °F to c °C or k K: c = k = f1.8
• c °C or k K to f °F: f = c × 1.8 = k × 1.8