Fahrenheit (°F)
Fahrenheit is a temperature scale in which water freezes at 32°F and boils at 212°F under standard atmospheric pressure. Named after German-Dutch physicist Daniel Gabriel Fahrenheit, it is the primary temperature scale used in the United States for weather, cooking, and everyday life. While most of the world has adopted Celsius, Fahrenheit remains deeply embedded in American culture - from thermostat settings to weather apps to oven dials.
Definition
The Fahrenheit scale sets the freezing point of water at 32°F and the boiling point at 212°F, both at standard atmospheric pressure of 101.325 kPa. This creates a 180-degree interval between the two points, compared to 100 degrees on the Celsius scale. To convert Fahrenheit to Celsius, subtract 32 and multiply by 5/9. To convert Celsius to Fahrenheit, multiply by 9/5 and add 32. Absolute zero, the coldest possible temperature, is −459.67°F (−273.15°C or 0 K).
History
Daniel Gabriel Fahrenheit developed his scale around 1724. He initially set three reference points: 0°F for the temperature of a brine solution (the coldest he could reliably reproduce in his laboratory), 32°F for the freezing point of plain water, and 96°F for human body temperature as he measured it. Later refinements shifted body temperature to approximately 98.6°F and fixed the boiling point of water at exactly 212°F, creating a scale with 180 degrees between freezing and boiling. Fahrenheit's scale was widely adopted across the English-speaking world and became the standard in the British Empire. During the metrication wave of the 20th century, the United Kingdom, Canada, Australia, and most other nations switched to Celsius. The United States remains the only major country where Fahrenheit is the dominant everyday temperature unit.
Common Uses
In the United States, Fahrenheit is used for all everyday temperature contexts. Weather forecasts report highs and lows in Fahrenheit, home thermostats are set in Fahrenheit (a typical setting is 68-72°F), and ovens display temperature in Fahrenheit (350°F is a common baking temperature). Pool temperatures, body temperatures, and food safety guidelines all reference Fahrenheit in American contexts. Medical professionals in the US report fever thresholds in Fahrenheit, with 100.4°F (38°C) generally considered a fever. A few US-associated territories and some Caribbean nations also use Fahrenheit.
Did You Know? Facts About Fahrenheit
- Fahrenheit chose brine (a mix of ice, water, and ammonium chloride) as his zero point because it was the coldest temperature he could consistently reproduce in his lab.
- Normal human body temperature is 98.6°F (37°C) - but this average, established in 1851, may be slightly outdated; modern studies suggest it has dropped to around 97.9°F.
- At −40°, Fahrenheit and Celsius are identical: −40°F = −40°C.
- The highest temperature ever recorded in the US was 134°F (56.7°C) at Furnace Creek, Death Valley, on July 10, 1913.
- The 180-degree span between freezing and boiling in Fahrenheit was not a coincidence - Fahrenheit admired the 180° of a half-circle and may have designed the scale around it.