# Definition:Fahrenheit

## Definition

Fahrenheit is a temperature scale.

Its two reference points are:

$32 \fahr$, which is set at the melting point of water.
$212 \fahr$, which is set at the boiling point of water, as defined at sea level and standard atmospheric pressure.

A temperature measured in Fahrenheit is often referred to as so many degrees Fahrenheit.

### Conversion Factors

 $\ds$  $\ds T \fahr$ Temperature in Fahrenheit $\ds$ $=$ $\ds T \cels \times \dfrac 9 5 + 32$ Temperature in Celsius

### Symbol

$\fahr$

The symbol for the degree Fahrenheit is $\fahr$.

The $\LaTeX$ code for $\fahr$ is \fahr .

## Source of Name

This entry was named for Daniel Gabriel Fahrenheit.

## Historical Note

The Fahrenheit scale is based on that proposed in $1724$ by the physicist Daniel Gabriel Fahrenheit.

He initially defined the lower reference point from the lowest temperature he could achieve, by mixing equal parts of ice and salt and establishing the temperature at which it melted.

The upper reference point, $96 \fahr$, was taken to be his best estimate of the temperature of the human body.

For scientific purposes it has been all but completely superseded by the Celsius scale.

By the end of the $20$th century, Fahrenheit was used as the official temperature scale only in the US and its unincorporated territories, the Bahamas, Belize, and the Cayman Islands.