Fahrenheit

The Fahrenheit scale is a <a href="/facts/Scale_of_temperature/b2D6632R">temperature scale</a> based on one proposed in 1724 by the physicist <a href="/facts/Daniel_Gabriel_Fahrenheit/81zb7NUE">Daniel Gabriel Fahrenheit</a> (1686–1736). It uses the degree Fahrenheit (symbol: °F) as the unit. Several accounts of how he originally defined his scale exist, but the original paper suggests the lower defining point, 0 °F, was established as the freezing <a href="/facts/Temperature/QyGe4gmj">temperature</a> of a solution of <a href="/facts/Brine/xsN2GcLF">brine</a> made from a mixture of water, <a href="/facts/Ice/BGvkKFjD">ice</a>, and <a href="/facts/Ammonium_chloride/SfXdntlv">ammonium chloride</a> (a <a href="/facts/Salt_(chemistry)/lsSKwGpn">salt</a>). The other limit established was his best estimate of the average <a href="/facts/Human_body_temperature/zbWKsEhF">human body temperature</a>, originally set at 90 °F, then 96 °F (about 2.6 °F less than the modern value due to a later redefinition of the scale).
For much of the 20th century, the Fahrenheit scale was defined by two fixed points with a 180 °F separation: the temperature at which pure water freezes was defined as 32 °F and the boiling point of water was defined to be 212 °F, both at <a href="/facts/Sea_level/mDhuI7Xe">sea level</a> and under <a href="/facts/Standard_atmospheric_pressure/aTbYALII">standard atmospheric pressure</a>. It is now formally defined using the <a href="/facts/Kelvin/E3trzC4C">Kelvin</a> scale.
It continues to be used in the United States (including its <a href="/facts/Unincorporated_territories_of_the_United_States/B9xxaPTo">unincorporated territories</a>), its <a href="/facts/Compact_of_Free_Association/AyCyg8WC">freely associated states</a> in the Western Pacific (<a href="/facts/Palau/sYXMGPbX">Palau</a>, the <a href="/facts/Federated_States_of_Micronesia/U9VGo9fh">Federated States of Micronesia</a> and the <a href="/facts/Marshall_Islands/rRV4U7oD">Marshall Islands</a>), the <a href="/facts/Cayman_Islands/exXQq3xA">Cayman Islands</a>, and <a href="/facts/Liberia/U99yfl2k">Liberia</a>.
Fahrenheit is commonly still used alongside the <a href="/facts/Celsius/okAEu1CA">Celsius</a> scale in other countries that use the U.S. <a href="/facts/Metrological/HC0MmLdb">metrological</a> service, such as <a href="/facts/Antigua_and_Barbuda/DXQrHm3x">Antigua and Barbuda</a>, <a href="/facts/Saint_Kitts_and_Nevis/SMPo2Ybr">Saint Kitts and Nevis</a>, the <a href="/facts/The_Bahamas/x6VKsUhj">Bahamas</a>, and <a href="/facts/Belize/2xVuhCTt">Belize</a>. A handful of <a href="/facts/British_Overseas_Territories/fUjVAy3E">British Overseas Territories</a>, including the <a href="/facts/British_Virgin_Islands/Wl66NGLT">Virgin Islands</a>, <a href="/facts/Montserrat/J9PjQ974">Montserrat</a>, <a href="/facts/Anguilla/FUQnwcFa">Anguilla</a>, and Bermuda, also still use both scales. All other countries now use <a href="/facts/Celsius/okAEu1CA">Celsius</a> ("centigrade" until 1948), which was invented 18 years after the Fahrenheit scale.

Fahrenheit open-in-new

Fahrenheit